<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:8db56459-804c-400b-ad67-4c887b4d55e0,g:37160a79-f53b-4460-b396-f44aae8b92d7-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.fortrea.com/role/CONDENSEDCONSOLIDATEDANDCOMBINEDSTATEMENTSOFOPERATIONSParenthetical" xlink:type="simple" xlink:href="ftre-20240331.xsd#CONDENSEDCONSOLIDATEDANDCOMBINEDSTATEMENTSOFOPERATIONSParenthetical"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/CONDENSEDCONSOLIDATEDANDCOMBINEDSTATEMENTSOFOPERATIONSParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_a6148d84-7ee8-4dc4-aa38-ad830fe38b4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_6ba07bf0-3cb9-4a0d-b85b-f9dcb6d9ac2a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_a6148d84-7ee8-4dc4-aa38-ad830fe38b4f" xlink:to="loc_us-gaap_StatementTable_6ba07bf0-3cb9-4a0d-b85b-f9dcb6d9ac2a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_e98a9f79-06cc-4738-aa5c-2f1f62435686" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_6ba07bf0-3cb9-4a0d-b85b-f9dcb6d9ac2a" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_e98a9f79-06cc-4738-aa5c-2f1f62435686" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_e98a9f79-06cc-4738-aa5c-2f1f62435686_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_e98a9f79-06cc-4738-aa5c-2f1f62435686" xlink:to="loc_us-gaap_RelatedPartyDomain_e98a9f79-06cc-4738-aa5c-2f1f62435686_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_ddd62417-aefa-4bc4-90af-e0358671467d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_e98a9f79-06cc-4738-aa5c-2f1f62435686" xlink:to="loc_us-gaap_RelatedPartyDomain_ddd62417-aefa-4bc4-90af-e0358671467d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_83b00126-f635-4e1b-8fdb-a86f7d2a8d15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_ddd62417-aefa-4bc4-90af-e0358671467d" xlink:to="loc_us-gaap_RelatedPartyMember_83b00126-f635-4e1b-8fdb-a86f7d2a8d15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_e4847eba-bf9c-43e2-a85e-560fc767b268" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_a6148d84-7ee8-4dc4-aa38-ad830fe38b4f" xlink:to="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_e4847eba-bf9c-43e2-a85e-560fc767b268" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/CONDENSEDCONSOLIDATEDANDCOMBINEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="simple" xlink:href="ftre-20240331.xsd#CONDENSEDCONSOLIDATEDANDCOMBINEDSTATEMENTSOFCHANGESINEQUITY"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/CONDENSEDCONSOLIDATEDANDCOMBINEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_01c3d385-edda-4880-b749-f8bc9740d4b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_f964ddaf-7120-47e0-b9aa-2608aba01830" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_01c3d385-edda-4880-b749-f8bc9740d4b1" xlink:to="loc_us-gaap_StatementTable_f964ddaf-7120-47e0-b9aa-2608aba01830" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_50881bf2-c157-47b5-bf0e-4b49988881aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f964ddaf-7120-47e0-b9aa-2608aba01830" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_50881bf2-c157-47b5-bf0e-4b49988881aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_50881bf2-c157-47b5-bf0e-4b49988881aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_50881bf2-c157-47b5-bf0e-4b49988881aa" xlink:to="loc_us-gaap_EquityComponentDomain_50881bf2-c157-47b5-bf0e-4b49988881aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_1f7ffb58-43a1-4d5d-b9dd-2fcacc668cb6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_50881bf2-c157-47b5-bf0e-4b49988881aa" xlink:to="loc_us-gaap_EquityComponentDomain_1f7ffb58-43a1-4d5d-b9dd-2fcacc668cb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_626919a7-deef-43b7-a740-812816201243" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f7ffb58-43a1-4d5d-b9dd-2fcacc668cb6" xlink:to="loc_us-gaap_CommonStockMember_626919a7-deef-43b7-a740-812816201243" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_0a798e5b-b158-49f9-aeb3-b8007a42f9dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f7ffb58-43a1-4d5d-b9dd-2fcacc668cb6" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_0a798e5b-b158-49f9-aeb3-b8007a42f9dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ParentCompanyInvestmentMember_6b5adb37-b19e-469a-8302-8a317852889e" xlink:href="ftre-20240331.xsd#ftre_ParentCompanyInvestmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f7ffb58-43a1-4d5d-b9dd-2fcacc668cb6" xlink:to="loc_ftre_ParentCompanyInvestmentMember_6b5adb37-b19e-469a-8302-8a317852889e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_5470661f-565c-4bb9-956d-7bad80b4e308" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f7ffb58-43a1-4d5d-b9dd-2fcacc668cb6" xlink:to="loc_us-gaap_RetainedEarningsMember_5470661f-565c-4bb9-956d-7bad80b4e308" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_ef664377-bf66-417c-a690-f0c3e4fd1613" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f7ffb58-43a1-4d5d-b9dd-2fcacc668cb6" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_ef664377-bf66-417c-a690-f0c3e4fd1613" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_1a46fb98-42ee-4b90-a62e-3e4f8e2d0010" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f964ddaf-7120-47e0-b9aa-2608aba01830" xlink:to="loc_srt_RestatementAxis_1a46fb98-42ee-4b90-a62e-3e4f8e2d0010" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_1a46fb98-42ee-4b90-a62e-3e4f8e2d0010_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_1a46fb98-42ee-4b90-a62e-3e4f8e2d0010" xlink:to="loc_srt_RestatementDomain_1a46fb98-42ee-4b90-a62e-3e4f8e2d0010_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_e0eb643b-5d8e-49b2-a935-5c4ed50b77bc" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_1a46fb98-42ee-4b90-a62e-3e4f8e2d0010" xlink:to="loc_srt_RestatementDomain_e0eb643b-5d8e-49b2-a935-5c4ed50b77bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_b72583b5-ee50-4495-8b8f-dfc5cf9a6219" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_e0eb643b-5d8e-49b2-a935-5c4ed50b77bc" xlink:to="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_b72583b5-ee50-4495-8b8f-dfc5cf9a6219" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01c3d385-edda-4880-b749-f8bc9740d4b1" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_5800c681-b5cd-4bf8-ae24-a5b63efa66ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_5800c681-b5cd-4bf8-ae24-a5b63efa66ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_c4a0fe46-ed3c-4b5b-8a3c-ceed07499afc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_us-gaap_StockholdersEquity_c4a0fe46-ed3c-4b5b-8a3c-ceed07499afc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_73299606-0951-4eb4-b594-fba8b17543a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_us-gaap_NetIncomeLoss_73299606-0951-4eb4-b594-fba8b17543a1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_98b17422-9076-48e5-8b23-43e3ec5e57a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_98b17422-9076-48e5-8b23-43e3ec5e57a7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_c2c33e64-6a28-40ba-8087-cc86a5f3bb80" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_c2c33e64-6a28-40ba-8087-cc86a5f3bb80" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_92566614-1e44-4c40-bebe-32f5af25e50a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_92566614-1e44-4c40-bebe-32f5af25e50a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_2b7f782c-e5d1-42f8-a22c-c44983a7af39" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_2b7f782c-e5d1-42f8-a22c-c44983a7af39" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_5127d53f-c6a2-47ea-b4f2-0bafd5ad8ac9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_us-gaap_StockholdersEquityOther_5127d53f-c6a2-47ea-b4f2-0bafd5ad8ac9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_NetTransfersFromToParentExcludingSpecialPayment_3e030122-ca92-480f-b6c6-0df4c3437439" xlink:href="ftre-20240331.xsd#ftre_NetTransfersFromToParentExcludingSpecialPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8dc3082e-5af7-4064-8708-c40192b7b57c" xlink:to="loc_ftre_NetTransfersFromToParentExcludingSpecialPayment_3e030122-ca92-480f-b6c6-0df4c3437439" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_ff4ad5c6-0ef6-48fb-9ed7-69ed4a2936e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_149ee533-5444-477c-be56-753fe04dd0b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/BASISOFFINANCIALSTATEMENTPREPARATIONDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#BASISOFFINANCIALSTATEMENTPREPARATIONDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/BASISOFFINANCIALSTATEMENTPREPARATIONDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_6db4a47e-ea5b-4466-98c8-418be973464c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:to="loc_us-gaap_ConcentrationRiskTable_6db4a47e-ea5b-4466-98c8-418be973464c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_9d6ab2f6-97db-4c35-bfa9-ee54123ca8b5" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_6db4a47e-ea5b-4466-98c8-418be973464c" xlink:to="loc_srt_MajorCustomersAxis_9d6ab2f6-97db-4c35-bfa9-ee54123ca8b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_9d6ab2f6-97db-4c35-bfa9-ee54123ca8b5_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_9d6ab2f6-97db-4c35-bfa9-ee54123ca8b5" xlink:to="loc_srt_NameOfMajorCustomerDomain_9d6ab2f6-97db-4c35-bfa9-ee54123ca8b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_9fe8c67f-c9f5-4ff4-9f42-2a0ccced3629" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_9d6ab2f6-97db-4c35-bfa9-ee54123ca8b5" xlink:to="loc_srt_NameOfMajorCustomerDomain_9fe8c67f-c9f5-4ff4-9f42-2a0ccced3629" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_CustomerOneMember_4fcb86ab-bd22-4047-afba-7afe29c46fec" xlink:href="ftre-20240331.xsd#ftre_CustomerOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_9fe8c67f-c9f5-4ff4-9f42-2a0ccced3629" xlink:to="loc_ftre_CustomerOneMember_4fcb86ab-bd22-4047-afba-7afe29c46fec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_CustomerTwoMember_de7f9d27-10c7-4149-abb9-e906ef32d4e2" xlink:href="ftre-20240331.xsd#ftre_CustomerTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_9fe8c67f-c9f5-4ff4-9f42-2a0ccced3629" xlink:to="loc_ftre_CustomerTwoMember_de7f9d27-10c7-4149-abb9-e906ef32d4e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_PharmaceuticalCompanyOneMember_498fdea0-bb18-4986-81d3-ba4ee732b976" xlink:href="ftre-20240331.xsd#ftre_PharmaceuticalCompanyOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_9fe8c67f-c9f5-4ff4-9f42-2a0ccced3629" xlink:to="loc_ftre_PharmaceuticalCompanyOneMember_498fdea0-bb18-4986-81d3-ba4ee732b976" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_PharmaceuticalCompanyTwoMember_407aa3e4-6b2f-483e-b9d3-d86f8f96c41b" xlink:href="ftre-20240331.xsd#ftre_PharmaceuticalCompanyTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_9fe8c67f-c9f5-4ff4-9f42-2a0ccced3629" xlink:to="loc_ftre_PharmaceuticalCompanyTwoMember_407aa3e4-6b2f-483e-b9d3-d86f8f96c41b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_df0767cc-e7cb-4bb2-aa88-583af0793138" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_6db4a47e-ea5b-4466-98c8-418be973464c" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_df0767cc-e7cb-4bb2-aa88-583af0793138" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_df0767cc-e7cb-4bb2-aa88-583af0793138_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_df0767cc-e7cb-4bb2-aa88-583af0793138" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_df0767cc-e7cb-4bb2-aa88-583af0793138_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_e6760c94-8a6a-4a9a-8dfd-213f6fd53390" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_df0767cc-e7cb-4bb2-aa88-583af0793138" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_e6760c94-8a6a-4a9a-8dfd-213f6fd53390" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_0ef1173a-e487-49bb-afe8-8e90c7ee2f5e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_e6760c94-8a6a-4a9a-8dfd-213f6fd53390" xlink:to="loc_us-gaap_AccountsReceivableMember_0ef1173a-e487-49bb-afe8-8e90c7ee2f5e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_4a60bbab-2b0c-4d9c-a000-3d21a0031c8d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_e6760c94-8a6a-4a9a-8dfd-213f6fd53390" xlink:to="loc_us-gaap_SalesRevenueNetMember_4a60bbab-2b0c-4d9c-a000-3d21a0031c8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_2c1c8dd0-6d05-491e-b7bc-82351076a5a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_6db4a47e-ea5b-4466-98c8-418be973464c" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_2c1c8dd0-6d05-491e-b7bc-82351076a5a3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_2c1c8dd0-6d05-491e-b7bc-82351076a5a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_2c1c8dd0-6d05-491e-b7bc-82351076a5a3" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_2c1c8dd0-6d05-491e-b7bc-82351076a5a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_767b9cec-77de-4721-885e-25f58fe06fcb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_2c1c8dd0-6d05-491e-b7bc-82351076a5a3" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_767b9cec-77de-4721-885e-25f58fe06fcb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_df27c6e0-4606-4ae6-8909-576a9b9ab8f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_767b9cec-77de-4721-885e-25f58fe06fcb" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_df27c6e0-4606-4ae6-8909-576a9b9ab8f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_99993c36-c4d0-49ff-86da-4644dd11d648" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_6db4a47e-ea5b-4466-98c8-418be973464c" xlink:to="loc_srt_RestatementAxis_99993c36-c4d0-49ff-86da-4644dd11d648" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_99993c36-c4d0-49ff-86da-4644dd11d648_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_99993c36-c4d0-49ff-86da-4644dd11d648" xlink:to="loc_srt_RestatementDomain_99993c36-c4d0-49ff-86da-4644dd11d648_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_6e1727a3-ee2a-4a3c-8891-e11e378e158c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_99993c36-c4d0-49ff-86da-4644dd11d648" xlink:to="loc_srt_RestatementDomain_6e1727a3-ee2a-4a3c-8891-e11e378e158c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodReclassificationAdjustmentMember_2876b1d2-0090-486e-94d4-1ee5d681b378" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodReclassificationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_6e1727a3-ee2a-4a3c-8891-e11e378e158c" xlink:to="loc_srt_RevisionOfPriorPeriodReclassificationAdjustmentMember_2876b1d2-0090-486e-94d4-1ee5d681b378" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_1484de3a-203f-4727-aa9c-27b77bef8195" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:to="loc_us-gaap_NumberOfReportableSegments_1484de3a-203f-4727-aa9c-27b77bef8195" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_7128e14f-1fa3-4ede-84df-5b78e8c0eeb3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:to="loc_us-gaap_NumberOfOperatingSegments_7128e14f-1fa3-4ede-84df-5b78e8c0eeb3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_NumberOfCountriesWithPrimaryOfficeLocations_09ded84b-320b-41eb-a98a-bfa4ba67e7d5" xlink:href="ftre-20240331.xsd#ftre_NumberOfCountriesWithPrimaryOfficeLocations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:to="loc_ftre_NumberOfCountriesWithPrimaryOfficeLocations_09ded84b-320b-41eb-a98a-bfa4ba67e7d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_6409af6f-5dd1-46ab-a7e7-947ed3359307" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_6409af6f-5dd1-46ab-a7e7-947ed3359307" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_ac702f5d-cce6-4e66-82f0-671f1123b9ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_ac702f5d-cce6-4e66-82f0-671f1123b9ae" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_9a2562d1-d229-4fef-96cb-c9ee4617a638" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:to="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_9a2562d1-d229-4fef-96cb-c9ee4617a638" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_7efdc050-4b3b-46ef-85f1-b66fd477025e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_d3cfd978-05c6-4835-8cf4-0e3568a0cde1" xlink:to="loc_us-gaap_InterestExpense_7efdc050-4b3b-46ef-85f1-b66fd477025e" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DISCONTINUEDOPERATIONSNarrativeDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DISCONTINUEDOPERATIONSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DISCONTINUEDOPERATIONSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_dc02ecbe-080d-4c1c-8d39-64ee6fc4955a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_620f1427-7c62-4eb3-8fd2-88325ae09873" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_dc02ecbe-080d-4c1c-8d39-64ee6fc4955a" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_620f1427-7c62-4eb3-8fd2-88325ae09873" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_dcbb6091-80fe-4477-8cfb-e92ce41ee6e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_620f1427-7c62-4eb3-8fd2-88325ae09873" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_dcbb6091-80fe-4477-8cfb-e92ce41ee6e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_dcbb6091-80fe-4477-8cfb-e92ce41ee6e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_dcbb6091-80fe-4477-8cfb-e92ce41ee6e4" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_dcbb6091-80fe-4477-8cfb-e92ce41ee6e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_eea57beb-5437-4a0d-8a17-a21eaac3870f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_dcbb6091-80fe-4477-8cfb-e92ce41ee6e4" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_eea57beb-5437-4a0d-8a17-a21eaac3870f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_b2b21936-a905-49fc-a430-c08659950462" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DiscontinuedOperationsHeldforsaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_eea57beb-5437-4a0d-8a17-a21eaac3870f" xlink:to="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_b2b21936-a905-49fc-a430-c08659950462" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_e6e87eb1-b069-451f-85d4-c72142028f7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_620f1427-7c62-4eb3-8fd2-88325ae09873" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_e6e87eb1-b069-451f-85d4-c72142028f7c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_e6e87eb1-b069-451f-85d4-c72142028f7c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_e6e87eb1-b069-451f-85d4-c72142028f7c" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_e6e87eb1-b069-451f-85d4-c72142028f7c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_55d17216-f2a2-4a9f-af0a-a6f6e47531b3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_e6e87eb1-b069-451f-85d4-c72142028f7c" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_55d17216-f2a2-4a9f-af0a-a6f6e47531b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_EnablingServicesSegmentDisposalMember_9184362e-cfd0-4619-a5b2-7983a9bbbd53" xlink:href="ftre-20240331.xsd#ftre_EnablingServicesSegmentDisposalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_55d17216-f2a2-4a9f-af0a-a6f6e47531b3" xlink:to="loc_ftre_EnablingServicesSegmentDisposalMember_9184362e-cfd0-4619-a5b2-7983a9bbbd53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_e1741a48-c816-45e0-9521-f96e3c5ddcd9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_dc02ecbe-080d-4c1c-8d39-64ee6fc4955a" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_e1741a48-c816-45e0-9521-f96e3c5ddcd9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationConsiderationCash_efea776b-8057-4989-b264-c7dfb9abc701" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationConsiderationCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_dc02ecbe-080d-4c1c-8d39-64ee6fc4955a" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationConsiderationCash_efea776b-8057-4989-b264-c7dfb9abc701" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationConsiderationLiability_2c3b48a8-486a-4936-8419-0920d11c4a14" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_dc02ecbe-080d-4c1c-8d39-64ee6fc4955a" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationConsiderationLiability_2c3b48a8-486a-4936-8419-0920d11c4a14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_efec37bc-cca3-4c82-a866-0cfab36003d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_dc02ecbe-080d-4c1c-8d39-64ee6fc4955a" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_efec37bc-cca3-4c82-a866-0cfab36003d4" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DISCONTINUEDOPERATIONSEarningsfromDiscontinuedOperationsDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DISCONTINUEDOPERATIONSEarningsfromDiscontinuedOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DISCONTINUEDOPERATIONSEarningsfromDiscontinuedOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_4a4120b9-7c93-4fa5-beca-01f31ba9ccd5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_056f3bec-4465-491c-b7bb-4edf467a0db7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_4a4120b9-7c93-4fa5-beca-01f31ba9ccd5" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_056f3bec-4465-491c-b7bb-4edf467a0db7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_54afcd23-3008-4160-af50-3331536fa13b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_056f3bec-4465-491c-b7bb-4edf467a0db7" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_54afcd23-3008-4160-af50-3331536fa13b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_54afcd23-3008-4160-af50-3331536fa13b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_54afcd23-3008-4160-af50-3331536fa13b" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_54afcd23-3008-4160-af50-3331536fa13b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_0b478a8d-9483-4493-89bc-ae643f2aa810" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_54afcd23-3008-4160-af50-3331536fa13b" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_0b478a8d-9483-4493-89bc-ae643f2aa810" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_de019768-20a0-4791-ab12-8e3f2de483a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DiscontinuedOperationsHeldforsaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_0b478a8d-9483-4493-89bc-ae643f2aa810" xlink:to="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_de019768-20a0-4791-ab12-8e3f2de483a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_86cd94bc-8c70-4706-b08e-2fffc9ca912c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_056f3bec-4465-491c-b7bb-4edf467a0db7" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_86cd94bc-8c70-4706-b08e-2fffc9ca912c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86cd94bc-8c70-4706-b08e-2fffc9ca912c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_86cd94bc-8c70-4706-b08e-2fffc9ca912c" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86cd94bc-8c70-4706-b08e-2fffc9ca912c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_22932de3-b9b7-49ba-8e73-7a7343b68519" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_86cd94bc-8c70-4706-b08e-2fffc9ca912c" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_22932de3-b9b7-49ba-8e73-7a7343b68519" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_EnablingServicesSegmentDisposalMember_51e7aefd-1b8f-4dbe-bd5e-eaf1cef2f151" xlink:href="ftre-20240331.xsd#ftre_EnablingServicesSegmentDisposalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_22932de3-b9b7-49ba-8e73-7a7343b68519" xlink:to="loc_ftre_EnablingServicesSegmentDisposalMember_51e7aefd-1b8f-4dbe-bd5e-eaf1cef2f151" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_36c697f0-19b2-4559-b4eb-9509c7226257" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_4a4120b9-7c93-4fa5-beca-01f31ba9ccd5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_36c697f0-19b2-4559-b4eb-9509c7226257" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract_f6bcebe7-a89d-4ee5-b076-9280957171bc" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_4a4120b9-7c93-4fa5-beca-01f31ba9ccd5" xlink:to="loc_ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract_f6bcebe7-a89d-4ee5-b076-9280957171bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_220f9692-78ec-4f5b-885b-48a6d6954b91" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract_f6bcebe7-a89d-4ee5-b076-9280957171bc" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_220f9692-78ec-4f5b-885b-48a6d6954b91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_4de6dd79-45b0-4451-ae20-9f36a534a56d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract_f6bcebe7-a89d-4ee5-b076-9280957171bc" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_4de6dd79-45b0-4451-ae20-9f36a534a56d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization_d3a1fa80-e94a-4ef8-823a-3c31f89b7643" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract_f6bcebe7-a89d-4ee5-b076-9280957171bc" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization_d3a1fa80-e94a-4ef8-823a-3c31f89b7643" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationAssetImpairmentCharges_d8385264-0cf3-41b3-b6c4-4b0c99be53f7" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationAssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract_f6bcebe7-a89d-4ee5-b076-9280957171bc" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationAssetImpairmentCharges_d8385264-0cf3-41b3-b6c4-4b0c99be53f7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationRestructuringAndOtherCharges_e9aba1b8-4d43-4fcf-8d3e-d5d94bbfe809" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationRestructuringAndOtherCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract_f6bcebe7-a89d-4ee5-b076-9280957171bc" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationRestructuringAndOtherCharges_e9aba1b8-4d43-4fcf-8d3e-d5d94bbfe809" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationCostsAndExpense_9fbde721-b3a8-4a8e-9773-dab9a4fdca8b" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationCostsAndExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupNotDiscontinuedOperationCostsAndExpensesAbstract_f6bcebe7-a89d-4ee5-b076-9280957171bc" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationCostsAndExpense_9fbde721-b3a8-4a8e-9773-dab9a4fdca8b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_254910e6-774f-4894-8571-a3ac07f20239" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_4a4120b9-7c93-4fa5-beca-01f31ba9ccd5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_254910e6-774f-4894-8571-a3ac07f20239" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpenseAbstract_59fa755f-8a64-47bb-8128-ec3de2c9f7c4" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_4a4120b9-7c93-4fa5-beca-01f31ba9ccd5" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpenseAbstract_59fa755f-8a64-47bb-8128-ec3de2c9f7c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationGainLossForeignCurrencyTransaction_57191c44-7cf1-492c-9c5f-89dd22317dda" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationGainLossForeignCurrencyTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpenseAbstract_59fa755f-8a64-47bb-8128-ec3de2c9f7c4" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationGainLossForeignCurrencyTransaction_57191c44-7cf1-492c-9c5f-89dd22317dda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodBeforeIncomeTax_f228fb6f-c4e3-48e5-a4eb-3cd9d7cfa471" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodBeforeIncomeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpenseAbstract_59fa755f-8a64-47bb-8128-ec3de2c9f7c4" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodBeforeIncomeTax_f228fb6f-c4e3-48e5-a4eb-3cd9d7cfa471" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriod_44e89733-a587-4664-aa06-10c2007706f2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpenseAbstract_59fa755f-8a64-47bb-8128-ec3de2c9f7c4" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriod_44e89733-a587-4664-aa06-10c2007706f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodNetOfTax_6d81b237-4c33-4d56-aab9-38235fc807e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ftre_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpenseAbstract_59fa755f-8a64-47bb-8128-ec3de2c9f7c4" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodNetOfTax_6d81b237-4c33-4d56-aab9-38235fc807e7" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DISCONTINUEDOPERATIONSSignificantClassesofAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DISCONTINUEDOPERATIONSSignificantClassesofAssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DISCONTINUEDOPERATIONSSignificantClassesofAssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_621d0ade-5b01-4519-9197-28a2e75c7498" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_621d0ade-5b01-4519-9197-28a2e75c7498" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_0bafbeef-205d-4a69-ad31-74dc810af104" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_621d0ade-5b01-4519-9197-28a2e75c7498" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_0bafbeef-205d-4a69-ad31-74dc810af104" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_0bafbeef-205d-4a69-ad31-74dc810af104_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_0bafbeef-205d-4a69-ad31-74dc810af104" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_0bafbeef-205d-4a69-ad31-74dc810af104_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_ffebab14-bcec-4a87-86be-bfaf1cecd50e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_0bafbeef-205d-4a69-ad31-74dc810af104" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_ffebab14-bcec-4a87-86be-bfaf1cecd50e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_f786c35a-0523-4ed4-a075-5a57b29f2491" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DiscontinuedOperationsHeldforsaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_ffebab14-bcec-4a87-86be-bfaf1cecd50e" xlink:to="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_f786c35a-0523-4ed4-a075-5a57b29f2491" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_0b45f4a9-2300-43ac-b0b8-bd4bad3b1a5e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_621d0ade-5b01-4519-9197-28a2e75c7498" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_0b45f4a9-2300-43ac-b0b8-bd4bad3b1a5e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_0b45f4a9-2300-43ac-b0b8-bd4bad3b1a5e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_0b45f4a9-2300-43ac-b0b8-bd4bad3b1a5e" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_0b45f4a9-2300-43ac-b0b8-bd4bad3b1a5e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_13d1afc6-1dce-42b0-91f5-660409b49ced" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_0b45f4a9-2300-43ac-b0b8-bd4bad3b1a5e" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_13d1afc6-1dce-42b0-91f5-660409b49ced" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_EnablingServicesSegmentDisposalMember_893cc85d-9eaa-4789-92ae-2c2ad8ffc206" xlink:href="ftre-20240331.xsd#ftre_EnablingServicesSegmentDisposalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_13d1afc6-1dce-42b0-91f5-660409b49ced" xlink:to="loc_ftre_EnablingServicesSegmentDisposalMember_893cc85d-9eaa-4789-92ae-2c2ad8ffc206" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_f1ce7ec4-8423-4a1b-88ad-07adffe317a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_f1ce7ec4-8423-4a1b-88ad-07adffe317a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents_7a40eeb7-3d86-48d3-a9f7-330628b41dd3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_f1ce7ec4-8423-4a1b-88ad-07adffe317a3" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents_7a40eeb7-3d86-48d3-a9f7-330628b41dd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet_eeb54571-efe3-4bb1-b3a1-b2228f170bd7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_f1ce7ec4-8423-4a1b-88ad-07adffe317a3" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet_eeb54571-efe3-4bb1-b3a1-b2228f170bd7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationPrepaidAndOtherAssetsCurrent_d0d1841e-f9dd-4203-90b7-da2574c10f2d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationPrepaidAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_f1ce7ec4-8423-4a1b-88ad-07adffe317a3" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationPrepaidAndOtherAssetsCurrent_d0d1841e-f9dd-4203-90b7-da2574c10f2d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent_d0395f66-8374-4a89-bc46-cc86664a2948" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_f1ce7ec4-8423-4a1b-88ad-07adffe317a3" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent_d0395f66-8374-4a89-bc46-cc86664a2948" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentNoncurrent_8fa383bd-51c7-49cb-ba61-7786b908c0b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentNoncurrent_8fa383bd-51c7-49cb-ba61-7786b908c0b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwillNoncurrent_f8406b48-efad-4d14-b6d9-33276fdd5b9e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwillNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwillNoncurrent_f8406b48-efad-4d14-b6d9-33276fdd5b9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationIntangibleAssetsNoncurrent_70b8c08b-3d83-4b71-b958-1236c9a237f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationIntangibleAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationIntangibleAssetsNoncurrent_70b8c08b-3d83-4b71-b958-1236c9a237f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets_389b3f9e-70dc-4c00-bea6-2674c30ac285" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets_389b3f9e-70dc-4c00-bea6-2674c30ac285" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_cbc5c74c-863a-4df0-9244-35a2008c3c85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_cbc5c74c-863a-4df0-9244-35a2008c3c85" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_4fbe09f4-24f7-430d-80be-5cfd53e24759" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_4fbe09f4-24f7-430d-80be-5cfd53e24759" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent_8519cfc0-b9e9-4dbf-b3e2-425e60446b43" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_4fbe09f4-24f7-430d-80be-5cfd53e24759" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent_8519cfc0-b9e9-4dbf-b3e2-425e60446b43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent_f7990ab8-432c-43b6-9536-38e4a26950c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_4fbe09f4-24f7-430d-80be-5cfd53e24759" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent_f7990ab8-432c-43b6-9536-38e4a26950c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationDeferredRevenueCurrent_b33297bc-91a7-46c8-8832-269f208f7e0f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationDeferredRevenueCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_4fbe09f4-24f7-430d-80be-5cfd53e24759" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationDeferredRevenueCurrent_b33297bc-91a7-46c8-8832-269f208f7e0f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationLeaseLiabilityCurrent_87d67948-bb5d-4527-83aa-07236585e2d7" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_4fbe09f4-24f7-430d-80be-5cfd53e24759" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationLeaseLiabilityCurrent_87d67948-bb5d-4527-83aa-07236585e2d7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent_2a0d63fc-00be-4e0c-8bcf-7c7210ef7e86" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrentAbstract_4fbe09f4-24f7-430d-80be-5cfd53e24759" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent_2a0d63fc-00be-4e0c-8bcf-7c7210ef7e86" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationLeaseLiabilityNoncurrent_f46d68bc-6319-4b1a-8c92-23ab50ccb2fd" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationLeaseLiabilityNoncurrent_f46d68bc-6319-4b1a-8c92-23ab50ccb2fd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities_c57e4b86-4a2e-489f-8fd2-8379b393fc68" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities_c57e4b86-4a2e-489f-8fd2-8379b393fc68" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_e22b728a-6522-4bd9-be41-a8bf0dfdaff7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_962b8895-1d6f-470a-be0c-c77a9c978515" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_e22b728a-6522-4bd9-be41-a8bf0dfdaff7" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DISCONTINUEDOPERATIONSScheduleofSelectedInformationonCashFlowsRelatedtoDiscontinuedOperationsDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DISCONTINUEDOPERATIONSScheduleofSelectedInformationonCashFlowsRelatedtoDiscontinuedOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DISCONTINUEDOPERATIONSScheduleofSelectedInformationonCashFlowsRelatedtoDiscontinuedOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_e1480b70-d901-4ed0-a85b-df07618035f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_592708a5-a725-4fab-8b8c-60a8cbe72e01" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_e1480b70-d901-4ed0-a85b-df07618035f5" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_592708a5-a725-4fab-8b8c-60a8cbe72e01" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_9105acc9-382a-4323-a61a-b324914bcad0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_592708a5-a725-4fab-8b8c-60a8cbe72e01" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_9105acc9-382a-4323-a61a-b324914bcad0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_9105acc9-382a-4323-a61a-b324914bcad0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_9105acc9-382a-4323-a61a-b324914bcad0" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_9105acc9-382a-4323-a61a-b324914bcad0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_5b5c02b9-11ff-403c-9fee-b3bca3ec8c0e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_9105acc9-382a-4323-a61a-b324914bcad0" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_5b5c02b9-11ff-403c-9fee-b3bca3ec8c0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_ad8fdfef-b499-4a7c-9f20-f6054b9a96c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DiscontinuedOperationsHeldforsaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_5b5c02b9-11ff-403c-9fee-b3bca3ec8c0e" xlink:to="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_ad8fdfef-b499-4a7c-9f20-f6054b9a96c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_c5cf730c-f2c1-498d-9676-f40a0a288db5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_592708a5-a725-4fab-8b8c-60a8cbe72e01" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_c5cf730c-f2c1-498d-9676-f40a0a288db5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_c5cf730c-f2c1-498d-9676-f40a0a288db5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_c5cf730c-f2c1-498d-9676-f40a0a288db5" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_c5cf730c-f2c1-498d-9676-f40a0a288db5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_d96a2aa6-fffd-4e8b-a714-8d422b2b8f30" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_c5cf730c-f2c1-498d-9676-f40a0a288db5" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_d96a2aa6-fffd-4e8b-a714-8d422b2b8f30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_EnablingServicesSegmentDisposalMember_d854b848-bbc0-49da-ad8b-869298b85d15" xlink:href="ftre-20240331.xsd#ftre_EnablingServicesSegmentDisposalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_d96a2aa6-fffd-4e8b-a714-8d422b2b8f30" xlink:to="loc_ftre_EnablingServicesSegmentDisposalMember_d854b848-bbc0-49da-ad8b-869298b85d15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization_c5043298-877e-40b3-bc27-00414479e0fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_e1480b70-d901-4ed0-a85b-df07618035f5" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationDepreciationAndAmortization_c5043298-877e-40b3-bc27-00414479e0fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DisposalGroupIncludingDiscontinuedOperationCapitalExpenditures_de72ce93-35a3-44d9-ad56-b48258a7d322" xlink:href="ftre-20240331.xsd#ftre_DisposalGroupIncludingDiscontinuedOperationCapitalExpenditures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_e1480b70-d901-4ed0-a85b-df07618035f5" xlink:to="loc_ftre_DisposalGroupIncludingDiscontinuedOperationCapitalExpenditures_de72ce93-35a3-44d9-ad56-b48258a7d322" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/REVENUESScheduleofRevenuebySegmentandGeographyDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#REVENUESScheduleofRevenuebySegmentandGeographyDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/REVENUESScheduleofRevenuebySegmentandGeographyDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_d2b6ffa0-2d07-40d9-800e-5c1ee60c15e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_79569a64-d58d-4b2e-8d86-730f7b435ece" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d2b6ffa0-2d07-40d9-800e-5c1ee60c15e1" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_79569a64-d58d-4b2e-8d86-730f7b435ece" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_27035b28-436a-4a5b-bb2a-8f59153af9d1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_79569a64-d58d-4b2e-8d86-730f7b435ece" xlink:to="loc_srt_StatementGeographicalAxis_27035b28-436a-4a5b-bb2a-8f59153af9d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_27035b28-436a-4a5b-bb2a-8f59153af9d1_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_27035b28-436a-4a5b-bb2a-8f59153af9d1" xlink:to="loc_srt_SegmentGeographicalDomain_27035b28-436a-4a5b-bb2a-8f59153af9d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_a9720953-5166-4462-9847-d0c28c922634" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_27035b28-436a-4a5b-bb2a-8f59153af9d1" xlink:to="loc_srt_SegmentGeographicalDomain_a9720953-5166-4462-9847-d0c28c922634" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NorthAmericaMember_86325bd6-b80e-411d-a167-fa03b5b63fc7" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NorthAmericaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_a9720953-5166-4462-9847-d0c28c922634" xlink:to="loc_srt_NorthAmericaMember_86325bd6-b80e-411d-a167-fa03b5b63fc7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EuropeMember_e58e03e0-d38d-48b6-ad39-08f613f4c96a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EuropeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_a9720953-5166-4462-9847-d0c28c922634" xlink:to="loc_srt_EuropeMember_e58e03e0-d38d-48b6-ad39-08f613f4c96a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_OtherGeographicalAreasMember_9f882549-0af6-41f8-aedc-e11a49efce93" xlink:href="ftre-20240331.xsd#ftre_OtherGeographicalAreasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_a9720953-5166-4462-9847-d0c28c922634" xlink:to="loc_ftre_OtherGeographicalAreasMember_9f882549-0af6-41f8-aedc-e11a49efce93" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e06de8f8-6a8a-4d5a-82c7-34d50c4037b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d2b6ffa0-2d07-40d9-800e-5c1ee60c15e1" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e06de8f8-6a8a-4d5a-82c7-34d50c4037b0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/REVENUESScheduleofCapitalizedContractCostDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#REVENUESScheduleofCapitalizedContractCostDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/REVENUESScheduleofCapitalizedContractCostDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostLineItems_55fcab0d-8476-4a6a-945d-77455c2f5398" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostTable_0ecd0985-ca04-4fd7-b73a-f346bc4f30a2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_55fcab0d-8476-4a6a-945d-77455c2f5398" xlink:to="loc_us-gaap_CapitalizedContractCostTable_0ecd0985-ca04-4fd7-b73a-f346bc4f30a2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAxis_cb6abf12-d607-4847-9cbd-d272b762176a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_0ecd0985-ca04-4fd7-b73a-f346bc4f30a2" xlink:to="loc_us-gaap_CapitalizedContractCostAxis_cb6abf12-d607-4847-9cbd-d272b762176a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostDomain_cb6abf12-d607-4847-9cbd-d272b762176a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CapitalizedContractCostAxis_cb6abf12-d607-4847-9cbd-d272b762176a" xlink:to="loc_us-gaap_CapitalizedContractCostDomain_cb6abf12-d607-4847-9cbd-d272b762176a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostDomain_95375d9e-b412-43dd-8d90-0d12d02f6f0b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CapitalizedContractCostAxis_cb6abf12-d607-4847-9cbd-d272b762176a" xlink:to="loc_us-gaap_CapitalizedContractCostDomain_95375d9e-b412-43dd-8d90-0d12d02f6f0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SalesCommissionAssetsMember_918298d4-0c1a-4443-9e0b-de0613301980" xlink:href="ftre-20240331.xsd#ftre_SalesCommissionAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostDomain_95375d9e-b412-43dd-8d90-0d12d02f6f0b" xlink:to="loc_ftre_SalesCommissionAssetsMember_918298d4-0c1a-4443-9e0b-de0613301980" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DeferredContractCostsMember_0ce9fb28-52cf-4b22-860e-65934e917c94" xlink:href="ftre-20240331.xsd#ftre_DeferredContractCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostDomain_95375d9e-b412-43dd-8d90-0d12d02f6f0b" xlink:to="loc_ftre_DeferredContractCostsMember_0ce9fb28-52cf-4b22-860e-65934e917c94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNet_736c0a78-2851-486a-8aca-e3e012acc6cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_55fcab0d-8476-4a6a-945d-77455c2f5398" xlink:to="loc_us-gaap_CapitalizedContractCostNet_736c0a78-2851-486a-8aca-e3e012acc6cb" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/REVENUESNarrativeDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#REVENUESNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/REVENUESNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAxis_75c492a4-18fd-4759-a7e9-f300aac2ce18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:to="loc_us-gaap_CapitalizedContractCostAxis_75c492a4-18fd-4759-a7e9-f300aac2ce18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostDomain_75c492a4-18fd-4759-a7e9-f300aac2ce18_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CapitalizedContractCostAxis_75c492a4-18fd-4759-a7e9-f300aac2ce18" xlink:to="loc_us-gaap_CapitalizedContractCostDomain_75c492a4-18fd-4759-a7e9-f300aac2ce18_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostDomain_41f722a5-de6e-467c-8b33-5713da57d0dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CapitalizedContractCostAxis_75c492a4-18fd-4759-a7e9-f300aac2ce18" xlink:to="loc_us-gaap_CapitalizedContractCostDomain_41f722a5-de6e-467c-8b33-5713da57d0dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SalesCommissionAssetsMember_28d915f9-0e9b-4742-b05a-390cda75e6b1" xlink:href="ftre-20240331.xsd#ftre_SalesCommissionAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostDomain_41f722a5-de6e-467c-8b33-5713da57d0dc" xlink:to="loc_ftre_SalesCommissionAssetsMember_28d915f9-0e9b-4742-b05a-390cda75e6b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DeferredContractCostsMember_2d835516-4994-4a97-a1bf-082bd952d541" xlink:href="ftre-20240331.xsd#ftre_DeferredContractCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostDomain_41f722a5-de6e-467c-8b33-5713da57d0dc" xlink:to="loc_ftre_DeferredContractCostsMember_2d835516-4994-4a97-a1bf-082bd952d541" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_d23d1860-a2bd-4e6b-b0ec-63ea4060fb60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_d23d1860-a2bd-4e6b-b0ec-63ea4060fb60" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_db5f7c16-8caa-4545-9ec0-cb960cb5983e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:to="loc_srt_RangeAxis_db5f7c16-8caa-4545-9ec0-cb960cb5983e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_db5f7c16-8caa-4545-9ec0-cb960cb5983e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_db5f7c16-8caa-4545-9ec0-cb960cb5983e" xlink:to="loc_srt_RangeMember_db5f7c16-8caa-4545-9ec0-cb960cb5983e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_66d063ee-463a-4b20-9ecb-5225004a1bd3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_db5f7c16-8caa-4545-9ec0-cb960cb5983e" xlink:to="loc_srt_RangeMember_66d063ee-463a-4b20-9ecb-5225004a1bd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_627862f2-bf7d-4527-bcdd-924403b7aee1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_66d063ee-463a-4b20-9ecb-5225004a1bd3" xlink:to="loc_srt_MinimumMember_627862f2-bf7d-4527-bcdd-924403b7aee1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ff73aad5-e34a-4af3-a7ea-cf0f28f34853" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_66d063ee-463a-4b20-9ecb-5225004a1bd3" xlink:to="loc_srt_MaximumMember_ff73aad5-e34a-4af3-a7ea-cf0f28f34853" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_5b7a5812-5188-497d-a513-911422928dfa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:to="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_5b7a5812-5188-497d-a513-911422928dfa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5b7a5812-5188-497d-a513-911422928dfa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_5b7a5812-5188-497d-a513-911422928dfa" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5b7a5812-5188-497d-a513-911422928dfa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5f24a532-cd51-4a70-9ae0-1e446e1b65b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_5b7a5812-5188-497d-a513-911422928dfa" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5f24a532-cd51-4a70-9ae0-1e446e1b65b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ChangeInScopeAndChangeInEstimatedEffortToCompleteContractMember_8fcd8ef8-04df-4196-a17f-40e81e6c7186" xlink:href="ftre-20240331.xsd#ftre_ChangeInScopeAndChangeInEstimatedEffortToCompleteContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5f24a532-cd51-4a70-9ae0-1e446e1b65b5" xlink:to="loc_ftre_ChangeInScopeAndChangeInEstimatedEffortToCompleteContractMember_8fcd8ef8-04df-4196-a17f-40e81e6c7186" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortization_34695641-7c09-4506-beab-32acb0e45db0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_CapitalizedContractCostAmortization_34695641-7c09-4506-beab-32acb0e45db0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3975b8d0-e170-4b8f-8335-bcb18db56a60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3975b8d0-e170-4b8f-8335-bcb18db56a60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_ac6974fe-6f7f-488a-aaaf-e8d9569e8eb3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_ac6974fe-6f7f-488a-aaaf-e8d9569e8eb3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_b1b38720-2419-4314-a918-3737b58319c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_b1b38720-2419-4314-a918-3737b58319c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_166c77f5-7b95-429c-9b88-d0c5d8b05fbf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_166c77f5-7b95-429c-9b88-d0c5d8b05fbf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_a0742283-1fdd-4a8f-a0ad-4c077b662160" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_a0742283-1fdd-4a8f-a0ad-4c077b662160" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d2dee872-5ea9-4b16-877a-c4220ca02fb2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d2dee872-5ea9-4b16-877a-c4220ca02fb2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_829a7d99-4622-4c4a-acfe-33afbe96c44a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_829a7d99-4622-4c4a-acfe-33afbe96c44a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_68aa43bb-9fb3-4d25-a501-4e03b8c4192e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_EarningsPerShareBasic_68aa43bb-9fb3-4d25-a501-4e03b8c4192e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AccountsReceivablePurchaseProgramMaximumFacilityAmount_0c3117e8-0e58-4f6a-8d0b-c4fc900daa02" xlink:href="ftre-20240331.xsd#ftre_AccountsReceivablePurchaseProgramMaximumFacilityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_ftre_AccountsReceivablePurchaseProgramMaximumFacilityAmount_0c3117e8-0e58-4f6a-8d0b-c4fc900daa02" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AccountsReceivableFactored_8466cfe0-0a2a-4e59-bed2-15814dc4936d" xlink:href="ftre-20240331.xsd#ftre_AccountsReceivableFactored"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_ftre_AccountsReceivableFactored_8466cfe0-0a2a-4e59-bed2-15814dc4936d" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/REVENUESNarrativeDetails_1" xlink:type="simple" xlink:href="ftre-20240331.xsd#REVENUESNarrativeDetails_1"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/REVENUESNarrativeDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAxis_75c492a4-18fd-4759-a7e9-f300aac2ce18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:to="loc_us-gaap_CapitalizedContractCostAxis_75c492a4-18fd-4759-a7e9-f300aac2ce18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostDomain_75c492a4-18fd-4759-a7e9-f300aac2ce18_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CapitalizedContractCostAxis_75c492a4-18fd-4759-a7e9-f300aac2ce18" xlink:to="loc_us-gaap_CapitalizedContractCostDomain_75c492a4-18fd-4759-a7e9-f300aac2ce18_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostDomain_41f722a5-de6e-467c-8b33-5713da57d0dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CapitalizedContractCostAxis_75c492a4-18fd-4759-a7e9-f300aac2ce18" xlink:to="loc_us-gaap_CapitalizedContractCostDomain_41f722a5-de6e-467c-8b33-5713da57d0dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SalesCommissionAssetsMember_28d915f9-0e9b-4742-b05a-390cda75e6b1" xlink:href="ftre-20240331.xsd#ftre_SalesCommissionAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostDomain_41f722a5-de6e-467c-8b33-5713da57d0dc" xlink:to="loc_ftre_SalesCommissionAssetsMember_28d915f9-0e9b-4742-b05a-390cda75e6b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DeferredContractCostsMember_2d835516-4994-4a97-a1bf-082bd952d541" xlink:href="ftre-20240331.xsd#ftre_DeferredContractCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostDomain_41f722a5-de6e-467c-8b33-5713da57d0dc" xlink:to="loc_ftre_DeferredContractCostsMember_2d835516-4994-4a97-a1bf-082bd952d541" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_db5f7c16-8caa-4545-9ec0-cb960cb5983e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:to="loc_srt_RangeAxis_db5f7c16-8caa-4545-9ec0-cb960cb5983e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_db5f7c16-8caa-4545-9ec0-cb960cb5983e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_db5f7c16-8caa-4545-9ec0-cb960cb5983e" xlink:to="loc_srt_RangeMember_db5f7c16-8caa-4545-9ec0-cb960cb5983e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_66d063ee-463a-4b20-9ecb-5225004a1bd3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_db5f7c16-8caa-4545-9ec0-cb960cb5983e" xlink:to="loc_srt_RangeMember_66d063ee-463a-4b20-9ecb-5225004a1bd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_627862f2-bf7d-4527-bcdd-924403b7aee1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_66d063ee-463a-4b20-9ecb-5225004a1bd3" xlink:to="loc_srt_MinimumMember_627862f2-bf7d-4527-bcdd-924403b7aee1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ff73aad5-e34a-4af3-a7ea-cf0f28f34853" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_66d063ee-463a-4b20-9ecb-5225004a1bd3" xlink:to="loc_srt_MaximumMember_ff73aad5-e34a-4af3-a7ea-cf0f28f34853" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_5b7a5812-5188-497d-a513-911422928dfa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_236169aa-0c91-424c-bd38-db0f5c1a22af" xlink:to="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_5b7a5812-5188-497d-a513-911422928dfa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5b7a5812-5188-497d-a513-911422928dfa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_5b7a5812-5188-497d-a513-911422928dfa" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5b7a5812-5188-497d-a513-911422928dfa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5f24a532-cd51-4a70-9ae0-1e446e1b65b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_5b7a5812-5188-497d-a513-911422928dfa" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5f24a532-cd51-4a70-9ae0-1e446e1b65b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ChangeInScopeAndChangeInEstimatedEffortToCompleteContractMember_8fcd8ef8-04df-4196-a17f-40e81e6c7186" xlink:href="ftre-20240331.xsd#ftre_ChangeInScopeAndChangeInEstimatedEffortToCompleteContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_5f24a532-cd51-4a70-9ae0-1e446e1b65b5" xlink:to="loc_ftre_ChangeInScopeAndChangeInEstimatedEffortToCompleteContractMember_8fcd8ef8-04df-4196-a17f-40e81e6c7186" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortization_34695641-7c09-4506-beab-32acb0e45db0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_CapitalizedContractCostAmortization_34695641-7c09-4506-beab-32acb0e45db0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3975b8d0-e170-4b8f-8335-bcb18db56a60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3975b8d0-e170-4b8f-8335-bcb18db56a60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_ac6974fe-6f7f-488a-aaaf-e8d9569e8eb3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_ac6974fe-6f7f-488a-aaaf-e8d9569e8eb3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_b1b38720-2419-4314-a918-3737b58319c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_b1b38720-2419-4314-a918-3737b58319c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_166c77f5-7b95-429c-9b88-d0c5d8b05fbf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_166c77f5-7b95-429c-9b88-d0c5d8b05fbf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_a0742283-1fdd-4a8f-a0ad-4c077b662160" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_a0742283-1fdd-4a8f-a0ad-4c077b662160" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d2dee872-5ea9-4b16-877a-c4220ca02fb2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d2dee872-5ea9-4b16-877a-c4220ca02fb2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_829a7d99-4622-4c4a-acfe-33afbe96c44a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_829a7d99-4622-4c4a-acfe-33afbe96c44a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_68aa43bb-9fb3-4d25-a501-4e03b8c4192e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_us-gaap_EarningsPerShareBasic_68aa43bb-9fb3-4d25-a501-4e03b8c4192e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AccountsReceivablePurchaseProgramMaximumFacilityAmount_0c3117e8-0e58-4f6a-8d0b-c4fc900daa02" xlink:href="ftre-20240331.xsd#ftre_AccountsReceivablePurchaseProgramMaximumFacilityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_ftre_AccountsReceivablePurchaseProgramMaximumFacilityAmount_0c3117e8-0e58-4f6a-8d0b-c4fc900daa02" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AccountsReceivableFactored_8466cfe0-0a2a-4e59-bed2-15814dc4936d" xlink:href="ftre-20240331.xsd#ftre_AccountsReceivableFactored"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_3fef56ac-e29d-46d2-af0e-79dbb81505f6" xlink:to="loc_ftre_AccountsReceivableFactored_8466cfe0-0a2a-4e59-bed2-15814dc4936d" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/RESTRUCTURINGANDOTHERCHARGESScheduleofRestructuringandOtherChargesDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#RESTRUCTURINGANDOTHERCHARGESScheduleofRestructuringandOtherChargesDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/RESTRUCTURINGANDOTHERCHARGESScheduleofRestructuringandOtherChargesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_e8f09bb5-c74a-46bd-81b3-f2f2117deb17" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_44d498f8-d5da-4a6b-a2f0-d3497978c8aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_e8f09bb5-c74a-46bd-81b3-f2f2117deb17" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_44d498f8-d5da-4a6b-a2f0-d3497978c8aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_6a103d86-c557-4368-9acc-8d7e5766ade1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_44d498f8-d5da-4a6b-a2f0-d3497978c8aa" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_6a103d86-c557-4368-9acc-8d7e5766ade1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_6a103d86-c557-4368-9acc-8d7e5766ade1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_6a103d86-c557-4368-9acc-8d7e5766ade1" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_6a103d86-c557-4368-9acc-8d7e5766ade1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_e6baa3af-614b-4a7b-a5d3-28fdabacbab5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_6a103d86-c557-4368-9acc-8d7e5766ade1" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_e6baa3af-614b-4a7b-a5d3-28fdabacbab5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_1aeb5b95-2048-4172-a73a-884468062844" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_e6baa3af-614b-4a7b-a5d3-28fdabacbab5" xlink:to="loc_us-gaap_EmployeeSeveranceMember_1aeb5b95-2048-4172-a73a-884468062844" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_FacilityCostMember_0b71ee84-b3e1-4e20-893e-2b4800018e9e" xlink:href="ftre-20240331.xsd#ftre_FacilityCostMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_e6baa3af-614b-4a7b-a5d3-28fdabacbab5" xlink:to="loc_ftre_FacilityCostMember_0b71ee84-b3e1-4e20-893e-2b4800018e9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveRollForward_d4c37ca9-b237-40a6-afea-c1a7bf9b4529" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringReserveRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_e8f09bb5-c74a-46bd-81b3-f2f2117deb17" xlink:to="loc_us-gaap_RestructuringReserveRollForward_d4c37ca9-b237-40a6-afea-c1a7bf9b4529" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_ead00f28-520a-4e3e-a989-aab7cc5023be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_d4c37ca9-b237-40a6-afea-c1a7bf9b4529" xlink:to="loc_us-gaap_RestructuringReserve_ead00f28-520a-4e3e-a989-aab7cc5023be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_dc8f9f17-39b5-4400-82f6-95b894f47680" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_d4c37ca9-b237-40a6-afea-c1a7bf9b4529" xlink:to="loc_us-gaap_RestructuringCharges_dc8f9f17-39b5-4400-82f6-95b894f47680" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveAccrualAdjustment1_b39b1551-2139-4530-823d-231b290758b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringReserveAccrualAdjustment1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_d4c37ca9-b237-40a6-afea-c1a7bf9b4529" xlink:to="loc_us-gaap_RestructuringReserveAccrualAdjustment1_b39b1551-2139-4530-823d-231b290758b9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_RestructuringReservePaymentAndOtherAdjustments_5cebf19b-ff85-4870-814a-c37b7de089e8" xlink:href="ftre-20240331.xsd#ftre_RestructuringReservePaymentAndOtherAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_d4c37ca9-b237-40a6-afea-c1a7bf9b4529" xlink:to="loc_ftre_RestructuringReservePaymentAndOtherAdjustments_5cebf19b-ff85-4870-814a-c37b7de089e8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_2f78c244-4d1d-4f54-a1c7-9df2ed0df627" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringReserve"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/EARNINGSLOSSPERSHAREAntidilutiveSecuritiesExcludedfromComputationDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#EARNINGSLOSSPERSHAREAntidilutiveSecuritiesExcludedfromComputationDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/EARNINGSLOSSPERSHAREAntidilutiveSecuritiesExcludedfromComputationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_6bc5a206-6372-4c6a-8ea7-cf8edf2735fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_4f402430-8e04-4d65-bb7f-6817fb47119b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_6bc5a206-6372-4c6a-8ea7-cf8edf2735fc" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_4f402430-8e04-4d65-bb7f-6817fb47119b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_7c9fc0f9-c394-4f35-ab02-d875139c98ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_4f402430-8e04-4d65-bb7f-6817fb47119b" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_7c9fc0f9-c394-4f35-ab02-d875139c98ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7c9fc0f9-c394-4f35-ab02-d875139c98ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_7c9fc0f9-c394-4f35-ab02-d875139c98ed" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7c9fc0f9-c394-4f35-ab02-d875139c98ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_e0fd144f-df11-40f9-9d54-c1b5309a1837" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_7c9fc0f9-c394-4f35-ab02-d875139c98ed" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_e0fd144f-df11-40f9-9d54-c1b5309a1837" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_25c97993-8c5e-4869-b63e-98aa77dcef9b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_e0fd144f-df11-40f9-9d54-c1b5309a1837" xlink:to="loc_us-gaap_EmployeeStockOptionMember_25c97993-8c5e-4869-b63e-98aa77dcef9b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_234c6aa6-a810-4399-90b0-7c23a6a8cdaa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_4f402430-8e04-4d65-bb7f-6817fb47119b" xlink:to="loc_us-gaap_AwardTypeAxis_234c6aa6-a810-4399-90b0-7c23a6a8cdaa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_234c6aa6-a810-4399-90b0-7c23a6a8cdaa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_234c6aa6-a810-4399-90b0-7c23a6a8cdaa" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_234c6aa6-a810-4399-90b0-7c23a6a8cdaa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5537ebd6-7272-4625-b6a1-14eaf10b6a53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_234c6aa6-a810-4399-90b0-7c23a6a8cdaa" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5537ebd6-7272-4625-b6a1-14eaf10b6a53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_f1160adb-30d8-4dd5-bcdb-fb79ad9dd620" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5537ebd6-7272-4625-b6a1-14eaf10b6a53" xlink:to="loc_us-gaap_EmployeeStockOptionMember_f1160adb-30d8-4dd5-bcdb-fb79ad9dd620" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_bc29ff80-419e-4e49-90f4-04824ca48508" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_6bc5a206-6372-4c6a-8ea7-cf8edf2735fc" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_bc29ff80-419e-4e49-90f4-04824ca48508" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_7eaf4ef8-a64e-45f1-ae9b-2e121bd8b6cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_6bc5a206-6372-4c6a-8ea7-cf8edf2735fc" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_7eaf4ef8-a64e-45f1-ae9b-2e121bd8b6cd" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/GOODWILLANDINTANGIBLEASSETSComponentsofIntangibleAssetsDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#GOODWILLANDINTANGIBLEASSETSComponentsofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/GOODWILLANDINTANGIBLEASSETSComponentsofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b7ecddd5-58a7-4cb1-8c90-c5de6a2a9062" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_6aa248a7-483b-49e1-8830-7299f353b4ec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b7ecddd5-58a7-4cb1-8c90-c5de6a2a9062" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_6aa248a7-483b-49e1-8830-7299f353b4ec" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_418e089b-3c22-45ed-ae21-4ce985859074" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_6aa248a7-483b-49e1-8830-7299f353b4ec" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_418e089b-3c22-45ed-ae21-4ce985859074" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_418e089b-3c22-45ed-ae21-4ce985859074_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_418e089b-3c22-45ed-ae21-4ce985859074" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_418e089b-3c22-45ed-ae21-4ce985859074_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1603f9cd-c2e6-4548-bb5a-f74aa1aaa52a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_418e089b-3c22-45ed-ae21-4ce985859074" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1603f9cd-c2e6-4548-bb5a-f74aa1aaa52a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_fde1f457-9f76-4903-992e-5cc1a67f30b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1603f9cd-c2e6-4548-bb5a-f74aa1aaa52a" xlink:to="loc_us-gaap_CustomerRelationshipsMember_fde1f457-9f76-4903-992e-5cc1a67f30b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_58987616-b2a2-4a92-b26e-d5341b8e55ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1603f9cd-c2e6-4548-bb5a-f74aa1aaa52a" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_58987616-b2a2-4a92-b26e-d5341b8e55ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_8546fe1a-c96a-41af-8882-b53136d7895c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1603f9cd-c2e6-4548-bb5a-f74aa1aaa52a" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_8546fe1a-c96a-41af-8882-b53136d7895c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_d473bf60-a473-4a78-9e98-73d83d07b3d0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b7ecddd5-58a7-4cb1-8c90-c5de6a2a9062" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_d473bf60-a473-4a78-9e98-73d83d07b3d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_ccea2d11-dfad-44be-ba5c-171eb974a96f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b7ecddd5-58a7-4cb1-8c90-c5de6a2a9062" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_ccea2d11-dfad-44be-ba5c-171eb974a96f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fa3f35fb-26cd-4811-afee-1fc13a901ef3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b7ecddd5-58a7-4cb1-8c90-c5de6a2a9062" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fa3f35fb-26cd-4811-afee-1fc13a901ef3" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DEBTNarrativeDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DEBTNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DEBTNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_e4c45358-a493-4bb4-8938-2229c01f2e5c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_DebtInstrumentTable_e4c45358-a493-4bb4-8938-2229c01f2e5c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_4d7a936f-58e5-4d3e-ab09-5c2190cdb457" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_e4c45358-a493-4bb4-8938-2229c01f2e5c" xlink:to="loc_us-gaap_DebtInstrumentAxis_4d7a936f-58e5-4d3e-ab09-5c2190cdb457" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4d7a936f-58e5-4d3e-ab09-5c2190cdb457_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_4d7a936f-58e5-4d3e-ab09-5c2190cdb457" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4d7a936f-58e5-4d3e-ab09-5c2190cdb457_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_d6244ef4-8899-4f21-be36-d8277e91ce15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_4d7a936f-58e5-4d3e-ab09-5c2190cdb457" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_d6244ef4-8899-4f21-be36-d8277e91ce15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_A75SeniorNotesDue2030Member_f53bf741-84bd-4dc9-9093-d4896a3de76b" xlink:href="ftre-20240331.xsd#ftre_A75SeniorNotesDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d6244ef4-8899-4f21-be36-d8277e91ce15" xlink:to="loc_ftre_A75SeniorNotesDue2030Member_f53bf741-84bd-4dc9-9093-d4896a3de76b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SeniorSecuredRevolvingCreditFacilityMember_b54b8ae8-d91b-47f2-926b-66c75a4e32f4" xlink:href="ftre-20240331.xsd#ftre_SeniorSecuredRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d6244ef4-8899-4f21-be36-d8277e91ce15" xlink:to="loc_ftre_SeniorSecuredRevolvingCreditFacilityMember_b54b8ae8-d91b-47f2-926b-66c75a4e32f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SeniorSecuredTermLoanAFacilityDue2028Member_d323fef2-698b-4f5d-b540-362b5b7c895c" xlink:href="ftre-20240331.xsd#ftre_SeniorSecuredTermLoanAFacilityDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d6244ef4-8899-4f21-be36-d8277e91ce15" xlink:to="loc_ftre_SeniorSecuredTermLoanAFacilityDue2028Member_d323fef2-698b-4f5d-b540-362b5b7c895c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SeniorSecuredTermLoanBFacilityDue2028Member_0659db8a-1555-4aaa-a08d-47cd89bda0dc" xlink:href="ftre-20240331.xsd#ftre_SeniorSecuredTermLoanBFacilityDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d6244ef4-8899-4f21-be36-d8277e91ce15" xlink:to="loc_ftre_SeniorSecuredTermLoanBFacilityDue2028Member_0659db8a-1555-4aaa-a08d-47cd89bda0dc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_86e221ce-af0c-4572-aab5-687655f1cb0f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_e4c45358-a493-4bb4-8938-2229c01f2e5c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_86e221ce-af0c-4572-aab5-687655f1cb0f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_86e221ce-af0c-4572-aab5-687655f1cb0f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_86e221ce-af0c-4572-aab5-687655f1cb0f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_86e221ce-af0c-4572-aab5-687655f1cb0f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6eb5544c-0325-4e3a-9a03-79eb95193d75" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_86e221ce-af0c-4572-aab5-687655f1cb0f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6eb5544c-0325-4e3a-9a03-79eb95193d75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_424739f9-966b-4e42-8c92-9160f7b19f9f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6eb5544c-0325-4e3a-9a03-79eb95193d75" xlink:to="loc_us-gaap_SeniorNotesMember_424739f9-966b-4e42-8c92-9160f7b19f9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_10c27ff3-ab7f-4d9d-bef1-b7b88ea71a22" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6eb5544c-0325-4e3a-9a03-79eb95193d75" xlink:to="loc_us-gaap_LineOfCreditMember_10c27ff3-ab7f-4d9d-bef1-b7b88ea71a22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_f6fe47b0-9312-4261-b304-e50bed5ef7a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6eb5544c-0325-4e3a-9a03-79eb95193d75" xlink:to="loc_us-gaap_SecuredDebtMember_f6fe47b0-9312-4261-b304-e50bed5ef7a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_744f7838-427f-440e-a58b-a0dfefae4b78" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_e4c45358-a493-4bb4-8938-2229c01f2e5c" xlink:to="loc_us-gaap_CreditFacilityAxis_744f7838-427f-440e-a58b-a0dfefae4b78" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_744f7838-427f-440e-a58b-a0dfefae4b78_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_744f7838-427f-440e-a58b-a0dfefae4b78" xlink:to="loc_us-gaap_CreditFacilityDomain_744f7838-427f-440e-a58b-a0dfefae4b78_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_3e24a2a5-a8ca-4915-a469-100b972f07be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_744f7838-427f-440e-a58b-a0dfefae4b78" xlink:to="loc_us-gaap_CreditFacilityDomain_3e24a2a5-a8ca-4915-a469-100b972f07be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_0c703ba9-0a72-4b10-8776-332c7c756636" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3e24a2a5-a8ca-4915-a469-100b972f07be" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_0c703ba9-0a72-4b10-8776-332c7c756636" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_e5fdda5d-6685-402e-bfd7-5a2a52b5c00f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3e24a2a5-a8ca-4915-a469-100b972f07be" xlink:to="loc_us-gaap_SecuredDebtMember_e5fdda5d-6685-402e-bfd7-5a2a52b5c00f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BridgeLoanMember_132c0e59-23fe-4776-a55a-a37e1974d6f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BridgeLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3e24a2a5-a8ca-4915-a469-100b972f07be" xlink:to="loc_us-gaap_BridgeLoanMember_132c0e59-23fe-4776-a55a-a37e1974d6f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_5302b273-8545-47f8-928e-0ccce44b8430" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3e24a2a5-a8ca-4915-a469-100b972f07be" xlink:to="loc_us-gaap_LetterOfCreditMember_5302b273-8545-47f8-928e-0ccce44b8430" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_d7ca372b-9991-47c8-b0f4-c9a82c71b97c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_d7ca372b-9991-47c8-b0f4-c9a82c71b97c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_e813d118-d93f-47c3-a89f-6f98c891effd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_e813d118-d93f-47c3-a89f-6f98c891effd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_6105fccf-b2fb-4258-a22d-4513c39ce4af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_6105fccf-b2fb-4258-a22d-4513c39ce4af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt_3616f7cf-1007-4a7b-895a-46f5ced76f7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt_3616f7cf-1007-4a7b-895a-46f5ced76f7c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_c3e6242b-bf7b-4e77-98b2-f2c594c43c2c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_DebtInstrumentTerm_c3e6242b-bf7b-4e77-98b2-f2c594c43c2c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_152794e4-2729-4e12-b8e9-0b6ebcb5c6d1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfSecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_152794e4-2729-4e12-b8e9-0b6ebcb5c6d1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_d6368fb4-3e1c-410b-99e4-6540991e5dac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_d6368fb4-3e1c-410b-99e4-6540991e5dac" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_7e440c27-a5e5-4b47-86e4-f178171d6b37" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_LineOfCredit_7e440c27-a5e5-4b47-86e4-f178171d6b37" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_136216d9-bb1d-45bb-bb15-8384030c9d78" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_136216d9-bb1d-45bb-bb15-8384030c9d78" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_LineOfCreditFacilityAnnualAgencyFee_4f8bd0f6-b6c0-47f0-a500-35612e66eeea" xlink:href="ftre-20240331.xsd#ftre_LineOfCreditFacilityAnnualAgencyFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_ftre_LineOfCreditFacilityAnnualAgencyFee_4f8bd0f6-b6c0-47f0-a500-35612e66eeea" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_c3307a89-9c28-4b73-a82e-1aeed740ceb7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c1e658c1-2e92-47c3-841c-5016528d77a8" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_c3307a89-9c28-4b73-a82e-1aeed740ceb7" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DEBTScheduleofDebtDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DEBTScheduleofDebtDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DEBTScheduleofDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_66f54fff-a353-4854-87d5-c176a2ed1f21" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_210f2206-32ce-4ea5-a38f-8d0666722970" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_66f54fff-a353-4854-87d5-c176a2ed1f21" xlink:to="loc_us-gaap_DebtInstrumentTable_210f2206-32ce-4ea5-a38f-8d0666722970" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_1b0406f4-524d-4d93-82f7-1dc6289f17fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_210f2206-32ce-4ea5-a38f-8d0666722970" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_1b0406f4-524d-4d93-82f7-1dc6289f17fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_1b0406f4-524d-4d93-82f7-1dc6289f17fd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_1b0406f4-524d-4d93-82f7-1dc6289f17fd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_1b0406f4-524d-4d93-82f7-1dc6289f17fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_1906c5b3-3edf-4f3d-bf42-088a155ca8e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_1b0406f4-524d-4d93-82f7-1dc6289f17fd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_1906c5b3-3edf-4f3d-bf42-088a155ca8e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_5c510d9d-bd64-4aa6-bc05-c28f26f8cacc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_1906c5b3-3edf-4f3d-bf42-088a155ca8e6" xlink:to="loc_us-gaap_LineOfCreditMember_5c510d9d-bd64-4aa6-bc05-c28f26f8cacc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_30637a7e-9751-443f-8f03-b1e538c45689" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_1906c5b3-3edf-4f3d-bf42-088a155ca8e6" xlink:to="loc_us-gaap_SeniorNotesMember_30637a7e-9751-443f-8f03-b1e538c45689" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_e24c7be0-db4b-42f5-8682-571499e104d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_210f2206-32ce-4ea5-a38f-8d0666722970" xlink:to="loc_us-gaap_CreditFacilityAxis_e24c7be0-db4b-42f5-8682-571499e104d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_e24c7be0-db4b-42f5-8682-571499e104d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_e24c7be0-db4b-42f5-8682-571499e104d4" xlink:to="loc_us-gaap_CreditFacilityDomain_e24c7be0-db4b-42f5-8682-571499e104d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_5d962ba4-ccb3-4571-8fce-5850a867d034" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_e24c7be0-db4b-42f5-8682-571499e104d4" xlink:to="loc_us-gaap_CreditFacilityDomain_5d962ba4-ccb3-4571-8fce-5850a867d034" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_8dd54985-1298-44ba-aa4d-b5bb4cf4182f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5d962ba4-ccb3-4571-8fce-5850a867d034" xlink:to="loc_us-gaap_SecuredDebtMember_8dd54985-1298-44ba-aa4d-b5bb4cf4182f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_fcc6f8b5-0142-4a23-9d8d-5a1ade7fbcc2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5d962ba4-ccb3-4571-8fce-5850a867d034" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_fcc6f8b5-0142-4a23-9d8d-5a1ade7fbcc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_f268aa01-4edc-4c07-bc92-42eaf9d70f67" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_210f2206-32ce-4ea5-a38f-8d0666722970" xlink:to="loc_us-gaap_DebtInstrumentAxis_f268aa01-4edc-4c07-bc92-42eaf9d70f67" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_f268aa01-4edc-4c07-bc92-42eaf9d70f67_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_f268aa01-4edc-4c07-bc92-42eaf9d70f67" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_f268aa01-4edc-4c07-bc92-42eaf9d70f67_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_655440bb-5728-414d-ac69-5c8cfd90156d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_f268aa01-4edc-4c07-bc92-42eaf9d70f67" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_655440bb-5728-414d-ac69-5c8cfd90156d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_A75SeniorNotesDue2030Member_8d99fb10-5ab2-40f3-892a-488e646b7761" xlink:href="ftre-20240331.xsd#ftre_A75SeniorNotesDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_655440bb-5728-414d-ac69-5c8cfd90156d" xlink:to="loc_ftre_A75SeniorNotesDue2030Member_8d99fb10-5ab2-40f3-892a-488e646b7761" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SeniorSecuredTermLoanAFacilityDue2028Member_7b24a748-d7be-4afe-8ef9-5c934c3e0e6f" xlink:href="ftre-20240331.xsd#ftre_SeniorSecuredTermLoanAFacilityDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_655440bb-5728-414d-ac69-5c8cfd90156d" xlink:to="loc_ftre_SeniorSecuredTermLoanAFacilityDue2028Member_7b24a748-d7be-4afe-8ef9-5c934c3e0e6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SeniorSecuredTermLoanBFacilityDue2028Member_72e527e4-e528-49b6-b3c3-4a77d5244709" xlink:href="ftre-20240331.xsd#ftre_SeniorSecuredTermLoanBFacilityDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_655440bb-5728-414d-ac69-5c8cfd90156d" xlink:to="loc_ftre_SeniorSecuredTermLoanBFacilityDue2028Member_72e527e4-e528-49b6-b3c3-4a77d5244709" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowingsAbstract_4ab20270-57ee-4a76-bf5a-23b4f502f841" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermBorrowingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_66f54fff-a353-4854-87d5-c176a2ed1f21" xlink:to="loc_us-gaap_ShortTermBorrowingsAbstract_4ab20270-57ee-4a76-bf5a-23b4f502f841" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_LongTermDebtGrossCurrentMaturities_435bc96a-d876-42ca-abea-6e94b28762c1" xlink:href="ftre-20240331.xsd#ftre_LongTermDebtGrossCurrentMaturities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermBorrowingsAbstract_4ab20270-57ee-4a76-bf5a-23b4f502f841" xlink:to="loc_ftre_LongTermDebtGrossCurrentMaturities_435bc96a-d876-42ca-abea-6e94b28762c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsCurrentNet_efbc7489-5d4c-4cef-abe0-a028c65c1b69" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsCurrentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermBorrowingsAbstract_4ab20270-57ee-4a76-bf5a-23b4f502f841" xlink:to="loc_us-gaap_DeferredFinanceCostsCurrentNet_efbc7489-5d4c-4cef-abe0-a028c65c1b69" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_07f5fcf5-d3ef-42f8-8fbe-6e2346c443d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermBorrowingsAbstract_4ab20270-57ee-4a76-bf5a-23b4f502f841" xlink:to="loc_us-gaap_LongTermDebtCurrent_07f5fcf5-d3ef-42f8-8fbe-6e2346c443d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsAbstract_c7d3e9de-cb37-497c-8e36-2f3e8ff0ebb2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_66f54fff-a353-4854-87d5-c176a2ed1f21" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsAbstract_c7d3e9de-cb37-497c-8e36-2f3e8ff0ebb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_LongTermDebtGrossExcludingCurrentMaturities_916a2bfa-0ba6-47e3-b2d0-97f791c6048b" xlink:href="ftre-20240331.xsd#ftre_LongTermDebtGrossExcludingCurrentMaturities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsAbstract_c7d3e9de-cb37-497c-8e36-2f3e8ff0ebb2" xlink:to="loc_ftre_LongTermDebtGrossExcludingCurrentMaturities_916a2bfa-0ba6-47e3-b2d0-97f791c6048b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_278abf85-51db-4012-b081-db0bdd4c7263" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNoncurrentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsAbstract_c7d3e9de-cb37-497c-8e36-2f3e8ff0ebb2" xlink:to="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_278abf85-51db-4012-b081-db0bdd4c7263" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_8510faec-0218-48a2-845b-2d80eb40066d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsAbstract_c7d3e9de-cb37-497c-8e36-2f3e8ff0ebb2" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_8510faec-0218-48a2-845b-2d80eb40066d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_22225500-1e17-42f0-9115-9d90dee69faa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsAbstract_c7d3e9de-cb37-497c-8e36-2f3e8ff0ebb2" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_22225500-1e17-42f0-9115-9d90dee69faa" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESScheduleofDerivativeInstrumentsDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESScheduleofDerivativeInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESScheduleofDerivativeInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90576182-dc81-4b53-aa99-d3c3ebaaf1f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_c9d327eb-69b1-4637-9ffe-dc89a175c578" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90576182-dc81-4b53-aa99-d3c3ebaaf1f0" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_c9d327eb-69b1-4637-9ffe-dc89a175c578" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_401b1a6b-1df1-4597-b2c8-ff08eee64a6c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_c9d327eb-69b1-4637-9ffe-dc89a175c578" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_401b1a6b-1df1-4597-b2c8-ff08eee64a6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_401b1a6b-1df1-4597-b2c8-ff08eee64a6c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_401b1a6b-1df1-4597-b2c8-ff08eee64a6c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_401b1a6b-1df1-4597-b2c8-ff08eee64a6c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_a5615854-27a8-4cb2-8132-68ee66f0a34c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_401b1a6b-1df1-4597-b2c8-ff08eee64a6c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_a5615854-27a8-4cb2-8132-68ee66f0a34c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_ed724181-63ab-4b43-ae83-b1ed8369d02f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a5615854-27a8-4cb2-8132-68ee66f0a34c" xlink:to="loc_us-gaap_InterestRateSwapMember_ed724181-63ab-4b43-ae83-b1ed8369d02f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_697c3133-1bf5-4cc0-9e35-2df86f47aff8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a5615854-27a8-4cb2-8132-68ee66f0a34c" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_697c3133-1bf5-4cc0-9e35-2df86f47aff8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_5e2a0699-9de9-400c-9e89-c2b914beee96" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_c9d327eb-69b1-4637-9ffe-dc89a175c578" xlink:to="loc_us-gaap_HedgingDesignationAxis_5e2a0699-9de9-400c-9e89-c2b914beee96" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_5e2a0699-9de9-400c-9e89-c2b914beee96_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_5e2a0699-9de9-400c-9e89-c2b914beee96" xlink:to="loc_us-gaap_HedgingDesignationDomain_5e2a0699-9de9-400c-9e89-c2b914beee96_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_f3a34a0d-5130-4b16-a75b-9b07c7a5d09b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_5e2a0699-9de9-400c-9e89-c2b914beee96" xlink:to="loc_us-gaap_HedgingDesignationDomain_f3a34a0d-5130-4b16-a75b-9b07c7a5d09b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_0a662a65-6f3b-4305-914f-519f29cbd005" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_f3a34a0d-5130-4b16-a75b-9b07c7a5d09b" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_0a662a65-6f3b-4305-914f-519f29cbd005" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_d9bf10ef-8686-4b58-9b27-ec6619246c6a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_f3a34a0d-5130-4b16-a75b-9b07c7a5d09b" xlink:to="loc_us-gaap_NondesignatedMember_d9bf10ef-8686-4b58-9b27-ec6619246c6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetNotSubjectToMasterNettingArrangement_09670104-39f0-4725-8575-d621960e66c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeAssetNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90576182-dc81-4b53-aa99-d3c3ebaaf1f0" xlink:to="loc_us-gaap_DerivativeAssetNotSubjectToMasterNettingArrangement_09670104-39f0-4725-8575-d621960e66c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityNotSubjectToMasterNettingArrangement_994cc79b-7a05-49bb-9ecb-448a6a213744" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLiabilityNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90576182-dc81-4b53-aa99-d3c3ebaaf1f0" xlink:to="loc_us-gaap_DerivativeLiabilityNotSubjectToMasterNettingArrangement_994cc79b-7a05-49bb-9ecb-448a6a213744" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_aeee5c9b-0031-4a51-96d8-553a8f1c9171" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90576182-dc81-4b53-aa99-d3c3ebaaf1f0" xlink:to="loc_us-gaap_DerivativeNotionalAmount_aeee5c9b-0031-4a51-96d8-553a8f1c9171" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESPretaxEffectsofCashFlowHedgesDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESPretaxEffectsofCashFlowHedgesDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESPretaxEffectsofCashFlowHedgesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_088f9dbd-1342-416e-9c3e-1c557415ce16" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_2ba722d6-0195-43ec-ac0b-35fd8fb8dda5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_088f9dbd-1342-416e-9c3e-1c557415ce16" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_2ba722d6-0195-43ec-ac0b-35fd8fb8dda5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_d442a1cb-833f-4210-af9f-58c744af1f1c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_2ba722d6-0195-43ec-ac0b-35fd8fb8dda5" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_d442a1cb-833f-4210-af9f-58c744af1f1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d442a1cb-833f-4210-af9f-58c744af1f1c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d442a1cb-833f-4210-af9f-58c744af1f1c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d442a1cb-833f-4210-af9f-58c744af1f1c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_33b21974-d034-43f9-a867-be80240d5614" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d442a1cb-833f-4210-af9f-58c744af1f1c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_33b21974-d034-43f9-a867-be80240d5614" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_e2d0bbe4-0ff4-4e69-990e-358ccd8725fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_33b21974-d034-43f9-a867-be80240d5614" xlink:to="loc_us-gaap_InterestRateSwapMember_e2d0bbe4-0ff4-4e69-990e-358ccd8725fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_6113de7f-e5af-4fa3-bc2d-cc3e2ac43063" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_088f9dbd-1342-416e-9c3e-1c557415ce16" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_6113de7f-e5af-4fa3-bc2d-cc3e2ac43063" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESReclassifiedfromOtherComprehensiveLossintoEarningsDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESReclassifiedfromOtherComprehensiveLossintoEarningsDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESReclassifiedfromOtherComprehensiveLossintoEarningsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_b88cde2e-f822-4f3a-a7fa-764edd52ffbd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_db52f1b2-0fac-47f1-bd3f-7198862c2f62" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_b88cde2e-f822-4f3a-a7fa-764edd52ffbd" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_db52f1b2-0fac-47f1-bd3f-7198862c2f62" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_5ab3902b-8f88-4e87-b30c-86f9c36c268c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_db52f1b2-0fac-47f1-bd3f-7198862c2f62" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_5ab3902b-8f88-4e87-b30c-86f9c36c268c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5ab3902b-8f88-4e87-b30c-86f9c36c268c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5ab3902b-8f88-4e87-b30c-86f9c36c268c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5ab3902b-8f88-4e87-b30c-86f9c36c268c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b4c9f5eb-e29c-493b-b588-93606f405c4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5ab3902b-8f88-4e87-b30c-86f9c36c268c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b4c9f5eb-e29c-493b-b588-93606f405c4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_8259597b-847f-45c5-9cd1-bac5612b76cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_b4c9f5eb-e29c-493b-b588-93606f405c4f" xlink:to="loc_us-gaap_InterestRateSwapMember_8259597b-847f-45c5-9cd1-bac5612b76cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_55659a7f-b43b-42a7-87fb-33bb0780b166" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_db52f1b2-0fac-47f1-bd3f-7198862c2f62" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_55659a7f-b43b-42a7-87fb-33bb0780b166" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_55659a7f-b43b-42a7-87fb-33bb0780b166_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_55659a7f-b43b-42a7-87fb-33bb0780b166" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_55659a7f-b43b-42a7-87fb-33bb0780b166_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_00fd4dc2-8ed7-44b6-9a32-85cf15a7a231" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_55659a7f-b43b-42a7-87fb-33bb0780b166" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_00fd4dc2-8ed7-44b6-9a32-85cf15a7a231" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseMember_7d3b3141-8f94-48be-b859-64e1435488cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_00fd4dc2-8ed7-44b6-9a32-85cf15a7a231" xlink:to="loc_us-gaap_InterestExpenseMember_7d3b3141-8f94-48be-b859-64e1435488cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_4c4740df-12d6-4155-8192-44bd67faafb2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_b88cde2e-f822-4f3a-a7fa-764edd52ffbd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_4c4740df-12d6-4155-8192-44bd67faafb2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESGainLossforDerivativeContractsNotDesignatedasHedgesDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESGainLossforDerivativeContractsNotDesignatedasHedgesDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESGainLossforDerivativeContractsNotDesignatedasHedgesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_f6fdb887-5cc8-4be8-a743-bd080242ebc3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_de0c1508-866f-4661-a26f-a7891b710346" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_f6fdb887-5cc8-4be8-a743-bd080242ebc3" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_de0c1508-866f-4661-a26f-a7891b710346" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_dd12f258-0ac5-4496-bb49-9993b8cd0bfb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_de0c1508-866f-4661-a26f-a7891b710346" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_dd12f258-0ac5-4496-bb49-9993b8cd0bfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_dd12f258-0ac5-4496-bb49-9993b8cd0bfb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_dd12f258-0ac5-4496-bb49-9993b8cd0bfb" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_dd12f258-0ac5-4496-bb49-9993b8cd0bfb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_53746a4e-1655-42e3-9e52-4dda0d118c86" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_dd12f258-0ac5-4496-bb49-9993b8cd0bfb" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_53746a4e-1655-42e3-9e52-4dda0d118c86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_731c1735-b1c2-4fe2-a5d5-e7ff1144068b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_53746a4e-1655-42e3-9e52-4dda0d118c86" xlink:to="loc_us-gaap_ForeignExchangeContractMember_731c1735-b1c2-4fe2-a5d5-e7ff1144068b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_e2b3c447-5501-42fb-b0a0-58d2967200d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_de0c1508-866f-4661-a26f-a7891b710346" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_e2b3c447-5501-42fb-b0a0-58d2967200d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_e2b3c447-5501-42fb-b0a0-58d2967200d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_e2b3c447-5501-42fb-b0a0-58d2967200d4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_e2b3c447-5501-42fb-b0a0-58d2967200d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_59209589-f59a-4d75-aece-368045fa0f05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_e2b3c447-5501-42fb-b0a0-58d2967200d4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_59209589-f59a-4d75-aece-368045fa0f05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyGainLossMember_ca54e9f8-0c2e-40b2-a3b5-6a3e030b95cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_59209589-f59a-4d75-aece-368045fa0f05" xlink:to="loc_us-gaap_ForeignCurrencyGainLossMember_ca54e9f8-0c2e-40b2-a3b5-6a3e030b95cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_e30e910f-f203-4108-90ff-9d4baead0913" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_f6fdb887-5cc8-4be8-a743-bd080242ebc3" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_e30e910f-f203-4108-90ff-9d4baead0913" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/PREFERREDSTOCKANDCOMMONSHAREHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#PREFERREDSTOCKANDCOMMONSHAREHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/PREFERREDSTOCKANDCOMMONSHAREHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9aca0879-67e9-4d70-b70d-ac11170433e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_eb8dce68-2552-4c27-8161-b65898b40706" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9aca0879-67e9-4d70-b70d-ac11170433e7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_eb8dce68-2552-4c27-8161-b65898b40706" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_13bc0382-98ca-4cf8-bc12-cbb3649966c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_eb8dce68-2552-4c27-8161-b65898b40706" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_13bc0382-98ca-4cf8-bc12-cbb3649966c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_13bc0382-98ca-4cf8-bc12-cbb3649966c8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_13bc0382-98ca-4cf8-bc12-cbb3649966c8" xlink:to="loc_us-gaap_EquityComponentDomain_13bc0382-98ca-4cf8-bc12-cbb3649966c8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_b202f6c6-0218-4f1b-814a-5b7c62613b2f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_13bc0382-98ca-4cf8-bc12-cbb3649966c8" xlink:to="loc_us-gaap_EquityComponentDomain_b202f6c6-0218-4f1b-814a-5b7c62613b2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1d656510-ed42-44a4-932f-868f2d998e18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_b202f6c6-0218-4f1b-814a-5b7c62613b2f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1d656510-ed42-44a4-932f-868f2d998e18" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_342aee9d-9206-401c-b047-99d040e56738" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1d656510-ed42-44a4-932f-868f2d998e18" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_342aee9d-9206-401c-b047-99d040e56738" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_a568c592-a9ef-4783-8dd3-b76767c9ff17" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1d656510-ed42-44a4-932f-868f2d998e18" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_a568c592-a9ef-4783-8dd3-b76767c9ff17" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_49abe63d-ed67-4b7c-a178-85a022246c2a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1d656510-ed42-44a4-932f-868f2d998e18" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_49abe63d-ed67-4b7c-a178-85a022246c2a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9d9d297e-983d-4d8b-96fc-3d9f97f0ec19" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9aca0879-67e9-4d70-b70d-ac11170433e7" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9d9d297e-983d-4d8b-96fc-3d9f97f0ec19" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_91d33e37-f9d6-41ff-b22f-f8b6d5d15045" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9d9d297e-983d-4d8b-96fc-3d9f97f0ec19" xlink:to="loc_us-gaap_StockholdersEquity_91d33e37-f9d6-41ff-b22f-f8b6d5d15045" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_4225130c-ea32-4493-b600-572b1ce5bca9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9d9d297e-983d-4d8b-96fc-3d9f97f0ec19" xlink:to="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_4225130c-ea32-4493-b600-572b1ce5bca9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_da8342e3-c71c-4e3a-bf7d-dcf52d69590c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9d9d297e-983d-4d8b-96fc-3d9f97f0ec19" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_da8342e3-c71c-4e3a-bf7d-dcf52d69590c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_bb924218-a456-496b-928d-422d1ea78362" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9d9d297e-983d-4d8b-96fc-3d9f97f0ec19" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_bb924218-a456-496b-928d-422d1ea78362" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_3f550430-c5b5-4ea3-b6ef-b9305817c0f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/STOCKCOMPENSATIONPLANSNarrativeDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#STOCKCOMPENSATIONPLANSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/STOCKCOMPENSATIONPLANSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c4822100-24e6-4493-8b79-19196c8f9a53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c4822100-24e6-4493-8b79-19196c8f9a53" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_a4f28c1d-112d-4d29-9325-9563bfc9df36" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c4822100-24e6-4493-8b79-19196c8f9a53" xlink:to="loc_us-gaap_AwardTypeAxis_a4f28c1d-112d-4d29-9325-9563bfc9df36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a4f28c1d-112d-4d29-9325-9563bfc9df36_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_a4f28c1d-112d-4d29-9325-9563bfc9df36" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a4f28c1d-112d-4d29-9325-9563bfc9df36_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4c766440-d286-4b83-9de1-673fa8f8aa97" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_a4f28c1d-112d-4d29-9325-9563bfc9df36" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4c766440-d286-4b83-9de1-673fa8f8aa97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_48934fc9-d8b2-44f8-920a-ed11b6e1cfad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4c766440-d286-4b83-9de1-673fa8f8aa97" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_48934fc9-d8b2-44f8-920a-ed11b6e1cfad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_7cb9b3d4-0887-4d13-b884-50a69639ac65" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4c766440-d286-4b83-9de1-673fa8f8aa97" xlink:to="loc_us-gaap_PerformanceSharesMember_7cb9b3d4-0887-4d13-b884-50a69639ac65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_01fe19a3-f8a9-4f18-aaad-225a6f10d1fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4c766440-d286-4b83-9de1-673fa8f8aa97" xlink:to="loc_us-gaap_EmployeeStockOptionMember_01fe19a3-f8a9-4f18-aaad-225a6f10d1fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_39528d6a-29d3-415e-bd89-b199f6ce9aaf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c4822100-24e6-4493-8b79-19196c8f9a53" xlink:to="loc_us-gaap_PlanNameAxis_39528d6a-29d3-415e-bd89-b199f6ce9aaf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_39528d6a-29d3-415e-bd89-b199f6ce9aaf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_39528d6a-29d3-415e-bd89-b199f6ce9aaf" xlink:to="loc_us-gaap_PlanNameDomain_39528d6a-29d3-415e-bd89-b199f6ce9aaf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_702f19ae-729b-45bd-bb0a-24e2b9b9d892" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_39528d6a-29d3-415e-bd89-b199f6ce9aaf" xlink:to="loc_us-gaap_PlanNameDomain_702f19ae-729b-45bd-bb0a-24e2b9b9d892" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_FortreasOmnibusIncentivePlanMember_4e1a86a3-5049-4045-90e9-fcc7f2ada054" xlink:href="ftre-20240331.xsd#ftre_FortreasOmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_702f19ae-729b-45bd-bb0a-24e2b9b9d892" xlink:to="loc_ftre_FortreasOmnibusIncentivePlanMember_4e1a86a3-5049-4045-90e9-fcc7f2ada054" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_FortreasEmployeeStockPurchasePlanMember_17710200-3d71-4b27-b7d0-f0a0a292c9ca" xlink:href="ftre-20240331.xsd#ftre_FortreasEmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_702f19ae-729b-45bd-bb0a-24e2b9b9d892" xlink:to="loc_ftre_FortreasEmployeeStockPurchasePlanMember_17710200-3d71-4b27-b7d0-f0a0a292c9ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_c4e14711-e2fd-4f92-b9d2-3a598f158071" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c4822100-24e6-4493-8b79-19196c8f9a53" xlink:to="loc_us-gaap_VestingAxis_c4e14711-e2fd-4f92-b9d2-3a598f158071" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_c4e14711-e2fd-4f92-b9d2-3a598f158071_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_c4e14711-e2fd-4f92-b9d2-3a598f158071" xlink:to="loc_us-gaap_VestingDomain_c4e14711-e2fd-4f92-b9d2-3a598f158071_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_72b76347-bfd2-4a3d-84cf-132161592a98" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_c4e14711-e2fd-4f92-b9d2-3a598f158071" xlink:to="loc_us-gaap_VestingDomain_72b76347-bfd2-4a3d-84cf-132161592a98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_0cbe2ea6-05d2-4118-865b-6fbdd0fadb59" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_72b76347-bfd2-4a3d-84cf-132161592a98" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_0cbe2ea6-05d2-4118-865b-6fbdd0fadb59" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_686c0e05-9948-4294-91e2-e389f8e921a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_72b76347-bfd2-4a3d-84cf-132161592a98" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_686c0e05-9948-4294-91e2-e389f8e921a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_2586a427-c417-4b5b-af19-964502fa0d2e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationAwardTrancheThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_72b76347-bfd2-4a3d-84cf-132161592a98" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_2586a427-c417-4b5b-af19-964502fa0d2e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedUponConversion_0566dde4-bd9e-48ef-864b-b03f8f63bb33" xlink:href="ftre-20240331.xsd#ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedUponConversion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedUponConversion_0566dde4-bd9e-48ef-864b-b03f8f63bb33" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_d7ccf3af-e17b-47ce-a640-79f6c0670cab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_d7ccf3af-e17b-47ce-a640-79f6c0670cab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_569e8e3a-41d2-474a-8173-df5006c5c296" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_569e8e3a-41d2-474a-8173-df5006c5c296" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_a6986e3d-c67a-46b9-8b9f-a1c6491f364a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_a6986e3d-c67a-46b9-8b9f-a1c6491f364a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_ea4621fb-4de4-4401-9ceb-e1515a648949" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_ea4621fb-4de4-4401-9ceb-e1515a648949" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardCliffVestingPeriod_6ba48ac9-1115-4d7a-8041-0892aa2470ad" xlink:href="ftre-20240331.xsd#ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardCliffVestingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardCliffVestingPeriod_6ba48ac9-1115-4d7a-8041-0892aa2470ad" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_eb6b4d29-a896-4daf-becd-e206219d2bb6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_eb6b4d29-a896-4daf-becd-e206219d2bb6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_390a769e-7c45-4bfd-add9-ec0ca2116338" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69fadaac-8d6c-4cc7-a490-403803334be4" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_390a769e-7c45-4bfd-add9-ec0ca2116338" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/STOCKCOMPENSATIONPLANSFairValueEstimatesDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#STOCKCOMPENSATIONPLANSFairValueEstimatesDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/STOCKCOMPENSATIONPLANSFairValueEstimatesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50512347-b456-4f07-a2e7-fb32ec366e3a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f90162ef-2b4b-4fa4-b50f-e5483b73964d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50512347-b456-4f07-a2e7-fb32ec366e3a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f90162ef-2b4b-4fa4-b50f-e5483b73964d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_94bfa9b8-5fef-4dbf-a11c-09a3cf7c6bed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f90162ef-2b4b-4fa4-b50f-e5483b73964d" xlink:to="loc_us-gaap_AwardTypeAxis_94bfa9b8-5fef-4dbf-a11c-09a3cf7c6bed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_94bfa9b8-5fef-4dbf-a11c-09a3cf7c6bed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_94bfa9b8-5fef-4dbf-a11c-09a3cf7c6bed" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_94bfa9b8-5fef-4dbf-a11c-09a3cf7c6bed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b241d592-0f77-46eb-af6e-a053e9702921" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_94bfa9b8-5fef-4dbf-a11c-09a3cf7c6bed" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b241d592-0f77-46eb-af6e-a053e9702921" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_7d7ff8eb-6475-4cab-9f4d-a90fd471198c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b241d592-0f77-46eb-af6e-a053e9702921" xlink:to="loc_us-gaap_EmployeeStockOptionMember_7d7ff8eb-6475-4cab-9f4d-a90fd471198c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_a8f5096f-8ecf-4e6f-bced-71b6a8a94711" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50512347-b456-4f07-a2e7-fb32ec366e3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_a8f5096f-8ecf-4e6f-bced-71b6a8a94711" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_d5ad1b66-c982-4274-96a5-827ddcd3c32d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50512347-b456-4f07-a2e7-fb32ec366e3a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_d5ad1b66-c982-4274-96a5-827ddcd3c32d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_4a515cd6-e62b-40d9-8181-ad637e862c22" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50512347-b456-4f07-a2e7-fb32ec366e3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_4a515cd6-e62b-40d9-8181-ad637e862c22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageVolatilityRate_4500b8b1-c9bc-4137-85ca-af672f78bc36" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50512347-b456-4f07-a2e7-fb32ec366e3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageVolatilityRate_4500b8b1-c9bc-4137-85ca-af672f78bc36" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_1bc00912-d484-43c2-bd8d-1679fd442832" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_50512347-b456-4f07-a2e7-fb32ec366e3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_1bc00912-d484-43c2-bd8d-1679fd442832" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/STOCKCOMPENSATIONPLANSRestrictedStockUnitsandPerformanceSharesDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#STOCKCOMPENSATIONPLANSRestrictedStockUnitsandPerformanceSharesDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/STOCKCOMPENSATIONPLANSRestrictedStockUnitsandPerformanceSharesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8ac4571-2fd3-46af-800b-71bbd71d814f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_bc7b9232-9f24-4c8c-b572-2787224c6196" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8ac4571-2fd3-46af-800b-71bbd71d814f" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_bc7b9232-9f24-4c8c-b572-2787224c6196" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_0f45fbe8-0f49-48dc-9107-e08a4ddd7f7d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_bc7b9232-9f24-4c8c-b572-2787224c6196" xlink:to="loc_us-gaap_AwardTypeAxis_0f45fbe8-0f49-48dc-9107-e08a4ddd7f7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0f45fbe8-0f49-48dc-9107-e08a4ddd7f7d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_0f45fbe8-0f49-48dc-9107-e08a4ddd7f7d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0f45fbe8-0f49-48dc-9107-e08a4ddd7f7d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_afe525ac-029c-4025-8276-2308d7869a33" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_0f45fbe8-0f49-48dc-9107-e08a4ddd7f7d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_afe525ac-029c-4025-8276-2308d7869a33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_ee79b362-9462-48ea-9cab-5e3d6a568fc4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_afe525ac-029c-4025-8276-2308d7869a33" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_ee79b362-9462-48ea-9cab-5e3d6a568fc4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_e06c55ce-d1be-4ac8-a62d-6c02667b969b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_afe525ac-029c-4025-8276-2308d7869a33" xlink:to="loc_us-gaap_PerformanceSharesMember_e06c55ce-d1be-4ac8-a62d-6c02667b969b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ae78b9ee-fa10-4aad-a9ea-359ff6d35302" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8ac4571-2fd3-46af-800b-71bbd71d814f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ae78b9ee-fa10-4aad-a9ea-359ff6d35302" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_7d30612e-c351-43df-8ac1-6d9324496de2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ae78b9ee-fa10-4aad-a9ea-359ff6d35302" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_7d30612e-c351-43df-8ac1-6d9324496de2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConvertedInPeriod_aaebe340-6c23-4113-87db-d828569f0be0" xlink:href="ftre-20240331.xsd#ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConvertedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ae78b9ee-fa10-4aad-a9ea-359ff6d35302" xlink:to="loc_ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConvertedInPeriod_aaebe340-6c23-4113-87db-d828569f0be0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9f4be4d8-7440-48f4-9e90-861772e22256" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ae78b9ee-fa10-4aad-a9ea-359ff6d35302" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9f4be4d8-7440-48f4-9e90-861772e22256" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_b10936b0-a244-4e7f-aac8-4f7757942df9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ae78b9ee-fa10-4aad-a9ea-359ff6d35302" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_b10936b0-a244-4e7f-aac8-4f7757942df9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_c1f6ea18-394e-4093-a3cb-bba8d526a04d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ae78b9ee-fa10-4aad-a9ea-359ff6d35302" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_c1f6ea18-394e-4093-a3cb-bba8d526a04d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_7ebd9627-831f-463b-b6f4-707aede062c0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6efe1cb2-e4d8-4ead-b39e-de1bec1d53e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8ac4571-2fd3-46af-800b-71bbd71d814f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6efe1cb2-e4d8-4ead-b39e-de1bec1d53e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_77a75828-554e-4248-869e-ca39c1ea04b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6efe1cb2-e4d8-4ead-b39e-de1bec1d53e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_77a75828-554e-4248-869e-ca39c1ea04b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConvertedInPeriodWeightedAverageGrantDateFairValue_a341c9cf-6da1-499b-b6bd-e362ee110826" xlink:href="ftre-20240331.xsd#ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConvertedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6efe1cb2-e4d8-4ead-b39e-de1bec1d53e4" xlink:to="loc_ftre_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsConvertedInPeriodWeightedAverageGrantDateFairValue_a341c9cf-6da1-499b-b6bd-e362ee110826" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_22962357-ed13-4f88-b0ff-ec1204ea9cb3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6efe1cb2-e4d8-4ead-b39e-de1bec1d53e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_22962357-ed13-4f88-b0ff-ec1204ea9cb3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_a483a1db-7cc1-4c04-9bc3-ebcbdada1e9b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6efe1cb2-e4d8-4ead-b39e-de1bec1d53e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_a483a1db-7cc1-4c04-9bc3-ebcbdada1e9b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_995c1d63-245e-49b4-b87e-2a904523a175" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6efe1cb2-e4d8-4ead-b39e-de1bec1d53e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_995c1d63-245e-49b4-b87e-2a904523a175" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_5132b777-1a7b-471f-a3c9-c26a9ec15bb9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/STOCKCOMPENSATIONPLANSShareBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#STOCKCOMPENSATIONPLANSShareBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/STOCKCOMPENSATIONPLANSShareBasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_756a347d-96bc-4b65-8c60-02869cf80177" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_5f05d642-45b0-4523-b8bd-24c76546ea35" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_756a347d-96bc-4b65-8c60-02869cf80177" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_5f05d642-45b0-4523-b8bd-24c76546ea35" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_95783aec-1a98-43f1-a6b8-fcbd43e23692" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_5f05d642-45b0-4523-b8bd-24c76546ea35" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_95783aec-1a98-43f1-a6b8-fcbd43e23692" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_95783aec-1a98-43f1-a6b8-fcbd43e23692_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_95783aec-1a98-43f1-a6b8-fcbd43e23692" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_95783aec-1a98-43f1-a6b8-fcbd43e23692_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_66fd68ba-2105-43dd-a512-07ab2afa2d6b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_95783aec-1a98-43f1-a6b8-fcbd43e23692" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_66fd68ba-2105-43dd-a512-07ab2afa2d6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_6be8d120-eccf-4132-9aac-5aa77d0e4e88" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_66fd68ba-2105-43dd-a512-07ab2afa2d6b" xlink:to="loc_us-gaap_CostOfSalesMember_6be8d120-eccf-4132-9aac-5aa77d0e4e88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_0e11a523-bb60-427f-b202-2a4c30e7b10e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_66fd68ba-2105-43dd-a512-07ab2afa2d6b" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_0e11a523-bb60-427f-b202-2a4c30e7b10e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_19748a91-4ee6-4121-a50b-919f64208637" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_756a347d-96bc-4b65-8c60-02869cf80177" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_19748a91-4ee6-4121-a50b-919f64208637" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_bab8a26b-d978-4163-ad8d-ee4f1fe3001a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_756a347d-96bc-4b65-8c60-02869cf80177" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_bab8a26b-d978-4163-ad8d-ee4f1fe3001a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/TRANSACTIONSWITHFORMERPARENTAllocationofGeneralCorporateandOtherExpensesDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#TRANSACTIONSWITHFORMERPARENTAllocationofGeneralCorporateandOtherExpensesDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/TRANSACTIONSWITHFORMERPARENTAllocationofGeneralCorporateandOtherExpensesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_ed4ece7f-dbe3-4e54-8cb6-b7aca73eb7a2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_17267a73-b69e-4279-83fe-a59721e773c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_ed4ece7f-dbe3-4e54-8cb6-b7aca73eb7a2" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_17267a73-b69e-4279-83fe-a59721e773c5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_13b6ff56-ed64-408b-9caa-fdc42e40123d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_17267a73-b69e-4279-83fe-a59721e773c5" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_13b6ff56-ed64-408b-9caa-fdc42e40123d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_13b6ff56-ed64-408b-9caa-fdc42e40123d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_13b6ff56-ed64-408b-9caa-fdc42e40123d" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_13b6ff56-ed64-408b-9caa-fdc42e40123d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_305a00c9-3f81-444f-b590-d0fbfd754915" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_13b6ff56-ed64-408b-9caa-fdc42e40123d" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_305a00c9-3f81-444f-b590-d0fbfd754915" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DirectCostsRelatedPartyMember_6d6a1cd2-16ed-400a-91db-2091610cf0fd" xlink:href="ftre-20240331.xsd#ftre_DirectCostsRelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_305a00c9-3f81-444f-b590-d0fbfd754915" xlink:to="loc_ftre_DirectCostsRelatedPartyMember_6d6a1cd2-16ed-400a-91db-2091610cf0fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SellingGeneralAndAdministrativeExpensesRelatedPartyMember_7a2eea78-4b2d-487e-9ee9-8e1965dfddf1" xlink:href="ftre-20240331.xsd#ftre_SellingGeneralAndAdministrativeExpensesRelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_305a00c9-3f81-444f-b590-d0fbfd754915" xlink:to="loc_ftre_SellingGeneralAndAdministrativeExpensesRelatedPartyMember_7a2eea78-4b2d-487e-9ee9-8e1965dfddf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_RestructuringAndOtherChargesRelatedPartyMember_5ae6806f-835e-4c03-9585-e97325539c6d" xlink:href="ftre-20240331.xsd#ftre_RestructuringAndOtherChargesRelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_305a00c9-3f81-444f-b590-d0fbfd754915" xlink:to="loc_ftre_RestructuringAndOtherChargesRelatedPartyMember_5ae6806f-835e-4c03-9585-e97325539c6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ForeignExchangeGainLossRelatedPartyMember_feb3e595-a45d-4ec5-960c-486c32396ead" xlink:href="ftre-20240331.xsd#ftre_ForeignExchangeGainLossRelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_305a00c9-3f81-444f-b590-d0fbfd754915" xlink:to="loc_ftre_ForeignExchangeGainLossRelatedPartyMember_feb3e595-a45d-4ec5-960c-486c32396ead" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAmountsOfTransaction_f1103724-47b5-48a9-b44e-32ed0a57219b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAmountsOfTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_ed4ece7f-dbe3-4e54-8cb6-b7aca73eb7a2" xlink:to="loc_us-gaap_RelatedPartyTransactionAmountsOfTransaction_f1103724-47b5-48a9-b44e-32ed0a57219b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/TRANSACTIONSWITHFORMERPARENTNarrativeDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#TRANSACTIONSWITHFORMERPARENTNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/TRANSACTIONSWITHFORMERPARENTNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_3cec45fd-2d7b-4222-9c7e-b94581b8c5aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ea4b6799-2990-4192-a7d9-fcc0c866ee82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3cec45fd-2d7b-4222-9c7e-b94581b8c5aa" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ea4b6799-2990-4192-a7d9-fcc0c866ee82" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_8def6af9-ba14-4d39-924a-3b7bde72de9e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ea4b6799-2990-4192-a7d9-fcc0c866ee82" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_8def6af9-ba14-4d39-924a-3b7bde72de9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_8def6af9-ba14-4d39-924a-3b7bde72de9e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_8def6af9-ba14-4d39-924a-3b7bde72de9e" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_8def6af9-ba14-4d39-924a-3b7bde72de9e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_cdbc377e-39e8-4db0-befa-16f5bc6679e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_8def6af9-ba14-4d39-924a-3b7bde72de9e" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_cdbc377e-39e8-4db0-befa-16f5bc6679e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_GeneralFinancingActivitiesMember_2baf77a2-1058-4e1c-b81b-a0910b9c5a70" xlink:href="ftre-20240331.xsd#ftre_GeneralFinancingActivitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_cdbc377e-39e8-4db0-befa-16f5bc6679e4" xlink:to="loc_ftre_GeneralFinancingActivitiesMember_2baf77a2-1058-4e1c-b81b-a0910b9c5a70" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_CorporateAllocationsMember_ca9498f3-d059-4f60-8c98-c8af6489a0f4" xlink:href="ftre-20240331.xsd#ftre_CorporateAllocationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_cdbc377e-39e8-4db0-befa-16f5bc6679e4" xlink:to="loc_ftre_CorporateAllocationsMember_ca9498f3-d059-4f60-8c98-c8af6489a0f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SubcontractServicesMember_1f4c2f9a-16cc-47f5-bef7-3f7d32ff5997" xlink:href="ftre-20240331.xsd#ftre_SubcontractServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_cdbc377e-39e8-4db0-befa-16f5bc6679e4" xlink:to="loc_ftre_SubcontractServicesMember_1f4c2f9a-16cc-47f5-bef7-3f7d32ff5997" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAmountsOfTransaction_50cce5b8-5ac0-4d64-ac81-d9918f077cda" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAmountsOfTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3cec45fd-2d7b-4222-9c7e-b94581b8c5aa" xlink:to="loc_us-gaap_RelatedPartyTransactionAmountsOfTransaction_50cce5b8-5ac0-4d64-ac81-d9918f077cda" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/TRANSACTIONSWITHFORMERPARENTNetTransfersToandFromLabcorpDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#TRANSACTIONSWITHFORMERPARENTNetTransfersToandFromLabcorpDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/TRANSACTIONSWITHFORMERPARENTNetTransfersToandFromLabcorpDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_450a2a3c-5ed7-4e8d-b85a-a411eb6aaf4a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_12cb7d31-fd0a-404d-820b-6d740c649d59" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_450a2a3c-5ed7-4e8d-b85a-a411eb6aaf4a" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_12cb7d31-fd0a-404d-820b-6d740c649d59" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_34af1e3e-9416-4dc0-8d1f-72ead5bd7877" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_12cb7d31-fd0a-404d-820b-6d740c649d59" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_34af1e3e-9416-4dc0-8d1f-72ead5bd7877" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_34af1e3e-9416-4dc0-8d1f-72ead5bd7877_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_34af1e3e-9416-4dc0-8d1f-72ead5bd7877" xlink:to="loc_us-gaap_RelatedPartyDomain_34af1e3e-9416-4dc0-8d1f-72ead5bd7877_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_337d28aa-3317-4237-b075-9caea1baf4b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_34af1e3e-9416-4dc0-8d1f-72ead5bd7877" xlink:to="loc_us-gaap_RelatedPartyDomain_337d28aa-3317-4237-b075-9caea1baf4b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_0c38f2b3-005c-4be0-adea-887f8218ef40" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_337d28aa-3317-4237-b075-9caea1baf4b0" xlink:to="loc_us-gaap_RelatedPartyMember_0c38f2b3-005c-4be0-adea-887f8218ef40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_6186954c-c540-4895-aeb4-f040ad4c8b94" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_12cb7d31-fd0a-404d-820b-6d740c649d59" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_6186954c-c540-4895-aeb4-f040ad4c8b94" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_6186954c-c540-4895-aeb4-f040ad4c8b94_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_6186954c-c540-4895-aeb4-f040ad4c8b94" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_6186954c-c540-4895-aeb4-f040ad4c8b94_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_fb83fd88-d88f-45c9-be29-f330174b3332" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_6186954c-c540-4895-aeb4-f040ad4c8b94" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_fb83fd88-d88f-45c9-be29-f330174b3332" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_GeneralFinancingActivitiesMember_8be2f8bc-d5be-4a7e-85ac-53d38aa37f3b" xlink:href="ftre-20240331.xsd#ftre_GeneralFinancingActivitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_fb83fd88-d88f-45c9-be29-f330174b3332" xlink:to="loc_ftre_GeneralFinancingActivitiesMember_8be2f8bc-d5be-4a7e-85ac-53d38aa37f3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_CorporateAllocationsMember_e1ec559a-41bf-406f-9c50-86e717e43bdd" xlink:href="ftre-20240331.xsd#ftre_CorporateAllocationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_fb83fd88-d88f-45c9-be29-f330174b3332" xlink:to="loc_ftre_CorporateAllocationsMember_e1ec559a-41bf-406f-9c50-86e717e43bdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_StockCompensationExpenseMember_829f237c-3569-4c78-9008-d4f7e2296a74" xlink:href="ftre-20240331.xsd#ftre_StockCompensationExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_fb83fd88-d88f-45c9-be29-f330174b3332" xlink:to="loc_ftre_StockCompensationExpenseMember_829f237c-3569-4c78-9008-d4f7e2296a74" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_NetTransfersFromToParent_3f68623e-c5bc-419e-ad32-51e23f9a8b92" xlink:href="ftre-20240331.xsd#ftre_NetTransfersFromToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_450a2a3c-5ed7-4e8d-b85a-a411eb6aaf4a" xlink:to="loc_ftre_NetTransfersFromToParent_3f68623e-c5bc-419e-ad32-51e23f9a8b92" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSBalanceSheetsDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSBalanceSheetsDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSBalanceSheetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_cd5076f2-fb1e-4306-a616-712cf7f931c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_53484814-5146-41c4-8685-2ae2792d344e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_cd5076f2-fb1e-4306-a616-712cf7f931c9" xlink:to="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_53484814-5146-41c4-8685-2ae2792d344e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_2c180a17-e2fc-4faa-90e3-c51d64c9f5d2" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_53484814-5146-41c4-8685-2ae2792d344e" xlink:to="loc_srt_RestatementAxis_2c180a17-e2fc-4faa-90e3-c51d64c9f5d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_2c180a17-e2fc-4faa-90e3-c51d64c9f5d2_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_2c180a17-e2fc-4faa-90e3-c51d64c9f5d2" xlink:to="loc_srt_RestatementDomain_2c180a17-e2fc-4faa-90e3-c51d64c9f5d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_2ae47aff-92ba-4606-b697-1e3d63a2ba8d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_2c180a17-e2fc-4faa-90e3-c51d64c9f5d2" xlink:to="loc_srt_RestatementDomain_2ae47aff-92ba-4606-b697-1e3d63a2ba8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioPreviouslyReportedMember_5a38b3b3-8f55-4e9c-813e-ef7e59e0c9f4" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioPreviouslyReportedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_2ae47aff-92ba-4606-b697-1e3d63a2ba8d" xlink:to="loc_srt_ScenarioPreviouslyReportedMember_5a38b3b3-8f55-4e9c-813e-ef7e59e0c9f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_118b73a2-f069-4593-8601-72bc3e401b96" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_2ae47aff-92ba-4606-b697-1e3d63a2ba8d" xlink:to="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_118b73a2-f069-4593-8601-72bc3e401b96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AsRestatedBeforeReclassificationAdjustmentsMember_8b9587c3-d3ab-4075-8a44-1f16f370cc25" xlink:href="ftre-20240331.xsd#ftre_AsRestatedBeforeReclassificationAdjustmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_2ae47aff-92ba-4606-b697-1e3d63a2ba8d" xlink:to="loc_ftre_AsRestatedBeforeReclassificationAdjustmentsMember_8b9587c3-d3ab-4075-8a44-1f16f370cc25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodReclassificationAdjustmentMember_79d09980-9f2e-488b-a7a2-e83e4392b2b4" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodReclassificationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_2ae47aff-92ba-4606-b697-1e3d63a2ba8d" xlink:to="loc_srt_RevisionOfPriorPeriodReclassificationAdjustmentMember_79d09980-9f2e-488b-a7a2-e83e4392b2b4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationTypeAxis_8b243664-aac0-40c1-b8dc-f5e51a584e84" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_53484814-5146-41c4-8685-2ae2792d344e" xlink:to="loc_us-gaap_ReclassificationTypeAxis_8b243664-aac0-40c1-b8dc-f5e51a584e84" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationTypeDomain_8b243664-aac0-40c1-b8dc-f5e51a584e84_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationTypeAxis_8b243664-aac0-40c1-b8dc-f5e51a584e84" xlink:to="loc_us-gaap_ReclassificationTypeDomain_8b243664-aac0-40c1-b8dc-f5e51a584e84_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationTypeDomain_4a08261d-48c5-40fa-a3a1-5b636063b615" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationTypeAxis_8b243664-aac0-40c1-b8dc-f5e51a584e84" xlink:to="loc_us-gaap_ReclassificationTypeDomain_4a08261d-48c5-40fa-a3a1-5b636063b615" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ReclassificationDiscontinuedOperationsMember_f1ba4363-b00b-41d0-99aa-25d06aba5dc6" xlink:href="ftre-20240331.xsd#ftre_ReclassificationDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationTypeDomain_4a08261d-48c5-40fa-a3a1-5b636063b615" xlink:to="loc_ftre_ReclassificationDiscontinuedOperationsMember_f1ba4363-b00b-41d0-99aa-25d06aba5dc6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_cd5076f2-fb1e-4306-a616-712cf7f931c9" xlink:to="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_aa52650b-78f2-495a-b14d-aa8eab418612" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:to="loc_us-gaap_AssetsCurrentAbstract_aa52650b-78f2-495a-b14d-aa8eab418612" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_996483e1-b72b-4b74-82ee-43ba7c18461e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_aa52650b-78f2-495a-b14d-aa8eab418612" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_996483e1-b72b-4b74-82ee-43ba7c18461e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AccountsReceivableAndContractWithCustomerAssetAfterAllowanceForCreditLossCurrent_e14d7e6a-f877-4b64-8028-6e9e9ad802c7" xlink:href="ftre-20240331.xsd#ftre_AccountsReceivableAndContractWithCustomerAssetAfterAllowanceForCreditLossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_aa52650b-78f2-495a-b14d-aa8eab418612" xlink:to="loc_ftre_AccountsReceivableAndContractWithCustomerAssetAfterAllowanceForCreditLossCurrent_e14d7e6a-f877-4b64-8028-6e9e9ad802c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_51e4a914-dda3-459f-90c1-7725f78b0c05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_aa52650b-78f2-495a-b14d-aa8eab418612" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_51e4a914-dda3-459f-90c1-7725f78b0c05" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent_9807c67a-0b45-40c9-8d0b-8ac7ef71cf77" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_aa52650b-78f2-495a-b14d-aa8eab418612" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent_9807c67a-0b45-40c9-8d0b-8ac7ef71cf77" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_4190e6bf-a85d-49ad-84a2-38a96f091946" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_aa52650b-78f2-495a-b14d-aa8eab418612" xlink:to="loc_us-gaap_AssetsCurrent_4190e6bf-a85d-49ad-84a2-38a96f091946" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_PropertyPlantAndEquipmentAndOperatingLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_8d021397-b542-4403-abaa-1676a1fb5ceb" xlink:href="ftre-20240331.xsd#ftre_PropertyPlantAndEquipmentAndOperatingLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:to="loc_ftre_PropertyPlantAndEquipmentAndOperatingLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_8d021397-b542-4403-abaa-1676a1fb5ceb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_db1713d6-ed2b-4a11-9a55-9b837cff1504" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:to="loc_us-gaap_Goodwill_db1713d6-ed2b-4a11-9a55-9b837cff1504" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ece7fbbf-d90c-4cba-a816-8416ef3fba60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ece7fbbf-d90c-4cba-a816-8416ef3fba60" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_821caf9c-85bf-4188-8c9a-ac78276da24f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_821caf9c-85bf-4188-8c9a-ac78276da24f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_f1ec3911-ebe5-4b98-a6aa-9949d51c6c37" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_f1ec3911-ebe5-4b98-a6aa-9949d51c6c37" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAssetsNoncurrent_4b8dc866-71df-4a44-a118-e07a672d7cda" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAssetsNoncurrent_4b8dc866-71df-4a44-a118-e07a672d7cda" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_371902ac-9762-4557-9250-606a7b8c3111" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_16ef3f38-4beb-4a77-ba62-6f1cfe3fb85c" xlink:to="loc_us-gaap_Assets_371902ac-9762-4557-9250-606a7b8c3111" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_cd5076f2-fb1e-4306-a616-712cf7f931c9" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_87618e9f-60e4-4d62-8d57-506df4c63d3a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:to="loc_us-gaap_AccountsPayableCurrent_87618e9f-60e4-4d62-8d57-506df4c63d3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_68556a43-5e53-4262-a5d2-fe938a74b08b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_68556a43-5e53-4262-a5d2-fe938a74b08b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_c3d840ea-06b9-4dd2-a9ca-ecaab25dd80c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_c3d840ea-06b9-4dd2-a9ca-ecaab25dd80c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_2c06008e-34c6-4b9f-8dc0-8a01833f0185" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:to="loc_us-gaap_LongTermDebtCurrent_2c06008e-34c6-4b9f-8dc0-8a01833f0185" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_db238ecc-407e-44cc-8605-eec1246c1b89" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_db238ecc-407e-44cc-8605-eec1246c1b89" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent_4b2d218c-2fef-430d-8378-3d523662f72e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent_4b2d218c-2fef-430d-8378-3d523662f72e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_3cb37453-5c5e-430a-a603-6c426d5111b3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_e059dcc9-81fd-4e86-8068-f3a7c1b5650f" xlink:to="loc_us-gaap_LiabilitiesCurrent_3cb37453-5c5e-430a-a603-6c426d5111b3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_9a8db158-204e-4da5-b689-888a7deccdfc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_9a8db158-204e-4da5-b689-888a7deccdfc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_748c7296-8f46-4497-aa35-53922e2d5570" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_748c7296-8f46-4497-aa35-53922e2d5570" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxesAndOtherTaxLiabilitiesNoncurrent_a31bdb23-5942-45f8-8212-475a1bd1d721" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxesAndOtherTaxLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_DeferredIncomeTaxesAndOtherTaxLiabilitiesNoncurrent_a31bdb23-5942-45f8-8212-475a1bd1d721" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_52af7fe4-4308-45a0-ad4d-bca10c44622a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_52af7fe4-4308-45a0-ad4d-bca10c44622a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationNoncurrent_7f9e6253-2de4-4628-a381-c1abce0b18fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationNoncurrent_7f9e6253-2de4-4628-a381-c1abce0b18fd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_34e79b2c-b83b-4394-9aea-799acaece36c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_Liabilities_34e79b2c-b83b-4394-9aea-799acaece36c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_d4b71404-d09e-4921-baa4-6e30749828c1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_CommitmentsAndContingencies_d4b71404-d09e-4921-baa4-6e30749828c1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_074a286f-7caa-40e5-9751-da03d3f038a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_074a286f-7caa-40e5-9751-da03d3f038a8" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_NetParentInvestment_abe4a322-1e65-4a0c-8239-25ab56c403a5" xlink:href="ftre-20240331.xsd#ftre_NetParentInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_074a286f-7caa-40e5-9751-da03d3f038a8" xlink:to="loc_ftre_NetParentInvestment_abe4a322-1e65-4a0c-8239-25ab56c403a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_b0c0a664-bc75-4fcd-ab8a-353dd633b812" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_074a286f-7caa-40e5-9751-da03d3f038a8" xlink:to="loc_us-gaap_CommonStockValue_b0c0a664-bc75-4fcd-ab8a-353dd633b812" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_c517a505-ba41-42dc-bcde-e631794bf1ec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_074a286f-7caa-40e5-9751-da03d3f038a8" xlink:to="loc_us-gaap_AdditionalPaidInCapital_c517a505-ba41-42dc-bcde-e631794bf1ec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_3325a0ca-1eb9-4669-ad77-73f12b7d3ea2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_074a286f-7caa-40e5-9751-da03d3f038a8" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_3325a0ca-1eb9-4669-ad77-73f12b7d3ea2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_53bbadd5-c22f-45f1-a21a-177ba4f2c175" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_074a286f-7caa-40e5-9751-da03d3f038a8" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_53bbadd5-c22f-45f1-a21a-177ba4f2c175" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_76e004d7-4d8e-4dfc-b33a-fdcf8443b211" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_074a286f-7caa-40e5-9751-da03d3f038a8" xlink:to="loc_us-gaap_StockholdersEquity_76e004d7-4d8e-4dfc-b33a-fdcf8443b211" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_cfc64a1a-2421-4889-b60d-ecc7d473911d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_01e2143e-5d61-4d12-b3a4-4d9f726eee23" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_cfc64a1a-2421-4889-b60d-ecc7d473911d" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofOperationsDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_b5aef5b6-0448-4882-b6a4-f90cd0359a89" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_b5aef5b6-0448-4882-b6a4-f90cd0359a89" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_6094c1b3-f558-42d7-8db9-b86f75a9fbed" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_b5aef5b6-0448-4882-b6a4-f90cd0359a89" xlink:to="loc_srt_RestatementAxis_6094c1b3-f558-42d7-8db9-b86f75a9fbed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_6094c1b3-f558-42d7-8db9-b86f75a9fbed_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_6094c1b3-f558-42d7-8db9-b86f75a9fbed" xlink:to="loc_srt_RestatementDomain_6094c1b3-f558-42d7-8db9-b86f75a9fbed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_5f252869-dcc9-49aa-959e-f2007a5c8f0e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_6094c1b3-f558-42d7-8db9-b86f75a9fbed" xlink:to="loc_srt_RestatementDomain_5f252869-dcc9-49aa-959e-f2007a5c8f0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioPreviouslyReportedMember_7624ed79-0be3-43d7-bc24-5a984384f626" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioPreviouslyReportedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_5f252869-dcc9-49aa-959e-f2007a5c8f0e" xlink:to="loc_srt_ScenarioPreviouslyReportedMember_7624ed79-0be3-43d7-bc24-5a984384f626" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_9cf966b0-5ecb-4265-859b-0ec3a14b14a2" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_5f252869-dcc9-49aa-959e-f2007a5c8f0e" xlink:to="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_9cf966b0-5ecb-4265-859b-0ec3a14b14a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AsRestatedBeforeReclassificationAdjustmentsMember_3fa784c6-ff6f-4375-a473-8273b82e5a78" xlink:href="ftre-20240331.xsd#ftre_AsRestatedBeforeReclassificationAdjustmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_5f252869-dcc9-49aa-959e-f2007a5c8f0e" xlink:to="loc_ftre_AsRestatedBeforeReclassificationAdjustmentsMember_3fa784c6-ff6f-4375-a473-8273b82e5a78" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodReclassificationAdjustmentMember_e76dc984-08e1-48e1-b2c3-7f6614ecb8f3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodReclassificationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_5f252869-dcc9-49aa-959e-f2007a5c8f0e" xlink:to="loc_srt_RevisionOfPriorPeriodReclassificationAdjustmentMember_e76dc984-08e1-48e1-b2c3-7f6614ecb8f3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationTypeAxis_74eba5cd-b6f6-4247-81d7-7f9739d5bc13" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_b5aef5b6-0448-4882-b6a4-f90cd0359a89" xlink:to="loc_us-gaap_ReclassificationTypeAxis_74eba5cd-b6f6-4247-81d7-7f9739d5bc13" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationTypeDomain_74eba5cd-b6f6-4247-81d7-7f9739d5bc13_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationTypeAxis_74eba5cd-b6f6-4247-81d7-7f9739d5bc13" xlink:to="loc_us-gaap_ReclassificationTypeDomain_74eba5cd-b6f6-4247-81d7-7f9739d5bc13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationTypeDomain_8dccce23-b2af-4944-868c-98ce317ffa05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationTypeAxis_74eba5cd-b6f6-4247-81d7-7f9739d5bc13" xlink:to="loc_us-gaap_ReclassificationTypeDomain_8dccce23-b2af-4944-868c-98ce317ffa05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ReclassificationDiscontinuedOperationsMember_eaa3bd51-206c-48ac-b864-ec0a4ee0b064" xlink:href="ftre-20240331.xsd#ftre_ReclassificationDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationTypeDomain_8dccce23-b2af-4944-868c-98ce317ffa05" xlink:to="loc_ftre_ReclassificationDiscontinuedOperationsMember_eaa3bd51-206c-48ac-b864-ec0a4ee0b064" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ReclassificationBasisOfPresentationMember_b4d06f9f-23fb-4240-be8f-f695321923d3" xlink:href="ftre-20240331.xsd#ftre_ReclassificationBasisOfPresentationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationTypeDomain_8dccce23-b2af-4944-868c-98ce317ffa05" xlink:to="loc_ftre_ReclassificationBasisOfPresentationMember_b4d06f9f-23fb-4240-be8f-f695321923d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c7587378-5948-4585-ab1e-b33389d21823" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c7587378-5948-4585-ab1e-b33389d21823" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_6fcaf503-ddba-4b27-ae7d-db48e9d202b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_6fcaf503-ddba-4b27-ae7d-db48e9d202b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_cd6f1adc-3d6e-4e39-82cb-065909933a2e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_6fcaf503-ddba-4b27-ae7d-db48e9d202b8" xlink:to="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_cd6f1adc-3d6e-4e39-82cb-065909933a2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_1cd1aa17-a2b6-498c-8860-974fa17dc358" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_6fcaf503-ddba-4b27-ae7d-db48e9d202b8" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_1cd1aa17-a2b6-498c-8860-974fa17dc358" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_ad28c58c-c280-48ff-b8cd-1deafa9985c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_6fcaf503-ddba-4b27-ae7d-db48e9d202b8" xlink:to="loc_us-gaap_DepreciationAndAmortization_ad28c58c-c280-48ff-b8cd-1deafa9985c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetImpairment_7c0d90b1-00bd-4d96-a9ee-ce06fece063b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GoodwillAndIntangibleAssetImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_6fcaf503-ddba-4b27-ae7d-db48e9d202b8" xlink:to="loc_us-gaap_GoodwillAndIntangibleAssetImpairment_7c0d90b1-00bd-4d96-a9ee-ce06fece063b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCosts_f6964314-c0de-4519-94a8-10ec18c91756" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_6fcaf503-ddba-4b27-ae7d-db48e9d202b8" xlink:to="loc_us-gaap_RestructuringCosts_f6964314-c0de-4519-94a8-10ec18c91756" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_82c01c99-ece1-4163-aa26-c0527437a0a6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_6fcaf503-ddba-4b27-ae7d-db48e9d202b8" xlink:to="loc_us-gaap_CostsAndExpenses_82c01c99-ece1-4163-aa26-c0527437a0a6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_4f11afdb-094f-4383-b00c-cb4c3ecc9ce8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_OperatingIncomeLoss_4f11afdb-094f-4383-b00c-cb4c3ecc9ce8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_f8dbc07f-9bd3-4764-a183-7bf47355e7d2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_f8dbc07f-9bd3-4764-a183-7bf47355e7d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNet_db50cf33-5a3d-45d1-b68d-f1f382d706d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestIncomeExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_f8dbc07f-9bd3-4764-a183-7bf47355e7d2" xlink:to="loc_us-gaap_InterestIncomeExpenseNet_db50cf33-5a3d-45d1-b68d-f1f382d706d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_937be743-5a17-4e35-a1e8-5c310851b2d0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_f8dbc07f-9bd3-4764-a183-7bf47355e7d2" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_937be743-5a17-4e35-a1e8-5c310851b2d0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_732ca4d6-fa6f-4706-b871-b47554f53793" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_f8dbc07f-9bd3-4764-a183-7bf47355e7d2" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_732ca4d6-fa6f-4706-b871-b47554f53793" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_78203aed-4bfd-4f47-a01f-a5689f68de87" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_78203aed-4bfd-4f47-a01f-a5689f68de87" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_040fd634-bb34-412e-ab60-3854e232a150" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_040fd634-bb34-412e-ab60-3854e232a150" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperations_874aafca-d341-4588-9409-24cf396cd9c7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperations_874aafca-d341-4588-9409-24cf396cd9c7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_b6d7b905-7122-4a92-ad16-6c1bfa0f1be3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_8ad73c7f-f56b-4bf4-9f43-f39e56c1a483" xlink:to="loc_us-gaap_EarningsPerShareAbstract_b6d7b905-7122-4a92-ad16-6c1bfa0f1be3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_6258091a-d1c5-4a95-bc67-23f46020a6e2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsPerBasicShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_b6d7b905-7122-4a92-ad16-6c1bfa0f1be3" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_6258091a-d1c5-4a95-bc67-23f46020a6e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare_9cf183a6-120e-4f82-bfcb-f3b69cebc089" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_b6d7b905-7122-4a92-ad16-6c1bfa0f1be3" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare_9cf183a6-120e-4f82-bfcb-f3b69cebc089" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_66ae4b81-88b9-423f-a067-2c53e9cd1103" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_b6d7b905-7122-4a92-ad16-6c1bfa0f1be3" xlink:to="loc_us-gaap_EarningsPerShareBasic_66ae4b81-88b9-423f-a067-2c53e9cd1103" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_d4bd1cba-9787-4bac-99bb-80715fea04f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_b6d7b905-7122-4a92-ad16-6c1bfa0f1be3" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_d4bd1cba-9787-4bac-99bb-80715fea04f8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_7edfe3b5-ddae-4d96-bd8e-90d0151067ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_b6d7b905-7122-4a92-ad16-6c1bfa0f1be3" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_7edfe3b5-ddae-4d96-bd8e-90d0151067ac" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_c4e00982-aff7-47fa-b424-6353501001cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_b6d7b905-7122-4a92-ad16-6c1bfa0f1be3" xlink:to="loc_us-gaap_EarningsPerShareDiluted_c4e00982-aff7-47fa-b424-6353501001cf" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_4fb43495-fa20-4f1a-af14-0102c63cff27" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_4fb43495-fa20-4f1a-af14-0102c63cff27" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_69350c86-9e42-4546-870b-de324e4d92ac" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_4fb43495-fa20-4f1a-af14-0102c63cff27" xlink:to="loc_srt_RestatementAxis_69350c86-9e42-4546-870b-de324e4d92ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_69350c86-9e42-4546-870b-de324e4d92ac_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_69350c86-9e42-4546-870b-de324e4d92ac" xlink:to="loc_srt_RestatementDomain_69350c86-9e42-4546-870b-de324e4d92ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_39e2be5f-490e-4cbe-997f-92d75416e355" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_69350c86-9e42-4546-870b-de324e4d92ac" xlink:to="loc_srt_RestatementDomain_39e2be5f-490e-4cbe-997f-92d75416e355" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioPreviouslyReportedMember_451a0cbf-93f2-40c0-a19f-f428194485d9" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioPreviouslyReportedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_39e2be5f-490e-4cbe-997f-92d75416e355" xlink:to="loc_srt_ScenarioPreviouslyReportedMember_451a0cbf-93f2-40c0-a19f-f428194485d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_50c2fd95-ca99-4176-a3a8-0fa7e6d1d281" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_39e2be5f-490e-4cbe-997f-92d75416e355" xlink:to="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_50c2fd95-ca99-4176-a3a8-0fa7e6d1d281" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_89d5c531-4a19-4300-915b-cf5c416cea21" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_NetIncomeLoss_89d5c531-4a19-4300-915b-cf5c416cea21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxPortionAttributableToParent_2ef582fc-fb21-4153-91b5-5f8ebb7e80eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxPortionAttributableToParent_2ef582fc-fb21-4153-91b5-5f8ebb7e80eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_5f306efa-c750-42d5-a771-d912c849c97f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_5f306efa-c750-42d5-a771-d912c849c97f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTaxParent_69232d1a-a374-4f24-ae56-5a29d75703f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTaxParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTaxParent_69232d1a-a374-4f24-ae56-5a29d75703f4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_4c126a26-7a9a-45c0-b8de-9748ec7756de" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_4c126a26-7a9a-45c0-b8de-9748ec7756de" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_361ccfec-f92c-4bd7-af40-28c2c029e9ec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_361ccfec-f92c-4bd7-af40-28c2c029e9ec" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_6d329c9b-f712-43f3-b0d1-04f746f8221b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_6d329c9b-f712-43f3-b0d1-04f746f8221b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_85b73fcf-6c72-47c3-bca9-7a39fea1e8f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_c5d47d95-3064-45c6-a0b4-2f88727678f1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_85b73fcf-6c72-47c3-bca9-7a39fea1e8f0" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSChangesinEquityDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSChangesinEquityDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSChangesinEquityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_b153cb1b-e24a-428c-9420-3a608709b671" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_8655fbc7-2e96-4a12-b853-d107a7f86e3a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_b153cb1b-e24a-428c-9420-3a608709b671" xlink:to="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_8655fbc7-2e96-4a12-b853-d107a7f86e3a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_870a07a9-605b-4d12-ab4d-fdd50d8c248a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_8655fbc7-2e96-4a12-b853-d107a7f86e3a" xlink:to="loc_srt_RestatementAxis_870a07a9-605b-4d12-ab4d-fdd50d8c248a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_870a07a9-605b-4d12-ab4d-fdd50d8c248a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_870a07a9-605b-4d12-ab4d-fdd50d8c248a" xlink:to="loc_srt_RestatementDomain_870a07a9-605b-4d12-ab4d-fdd50d8c248a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_0df476df-f1a2-4829-89da-45274d6c5f6b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_870a07a9-605b-4d12-ab4d-fdd50d8c248a" xlink:to="loc_srt_RestatementDomain_0df476df-f1a2-4829-89da-45274d6c5f6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioPreviouslyReportedMember_94f05576-391c-494c-bd0d-d6fb61be3e4e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioPreviouslyReportedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_0df476df-f1a2-4829-89da-45274d6c5f6b" xlink:to="loc_srt_ScenarioPreviouslyReportedMember_94f05576-391c-494c-bd0d-d6fb61be3e4e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_362c07df-d758-4383-a69c-755d75b3a779" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_0df476df-f1a2-4829-89da-45274d6c5f6b" xlink:to="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_362c07df-d758-4383-a69c-755d75b3a779" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_55596abc-ec27-42ec-9f0a-81dd9bfce882" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_8655fbc7-2e96-4a12-b853-d107a7f86e3a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_55596abc-ec27-42ec-9f0a-81dd9bfce882" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_55596abc-ec27-42ec-9f0a-81dd9bfce882_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_55596abc-ec27-42ec-9f0a-81dd9bfce882" xlink:to="loc_us-gaap_EquityComponentDomain_55596abc-ec27-42ec-9f0a-81dd9bfce882_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_8df2ffa1-9777-4b9a-9819-743769c0ea1f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_55596abc-ec27-42ec-9f0a-81dd9bfce882" xlink:to="loc_us-gaap_EquityComponentDomain_8df2ffa1-9777-4b9a-9819-743769c0ea1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_f06f59b2-7420-4c78-a360-ef2623eb341c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8df2ffa1-9777-4b9a-9819-743769c0ea1f" xlink:to="loc_us-gaap_CommonStockMember_f06f59b2-7420-4c78-a360-ef2623eb341c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_cf698b78-6bd3-4909-b17f-0e7a605719ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8df2ffa1-9777-4b9a-9819-743769c0ea1f" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_cf698b78-6bd3-4909-b17f-0e7a605719ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ParentCompanyInvestmentMember_8cc2db75-b0b1-4c94-83e4-7ac247fd9ad7" xlink:href="ftre-20240331.xsd#ftre_ParentCompanyInvestmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8df2ffa1-9777-4b9a-9819-743769c0ea1f" xlink:to="loc_ftre_ParentCompanyInvestmentMember_8cc2db75-b0b1-4c94-83e4-7ac247fd9ad7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_438300d6-0011-4ac4-bf0a-3d9681bee61d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8df2ffa1-9777-4b9a-9819-743769c0ea1f" xlink:to="loc_us-gaap_RetainedEarningsMember_438300d6-0011-4ac4-bf0a-3d9681bee61d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_ece0cf11-5c41-46b1-be32-fc2b4246669a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8df2ffa1-9777-4b9a-9819-743769c0ea1f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_ece0cf11-5c41-46b1-be32-fc2b4246669a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_b153cb1b-e24a-428c-9420-3a608709b671" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_3b9a3672-4976-4a54-9c5f-524a3c40e26b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_3b9a3672-4976-4a54-9c5f-524a3c40e26b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_884d830c-8458-47a6-ab98-b677774fc68e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_us-gaap_StockholdersEquity_884d830c-8458-47a6-ab98-b677774fc68e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_0203dd8a-8b7e-4e3f-a2ae-3dded3a9fa99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_us-gaap_NetIncomeLoss_0203dd8a-8b7e-4e3f-a2ae-3dded3a9fa99" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_0dc29f33-9adb-4922-8ade-44c2cb6937c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_0dc29f33-9adb-4922-8ade-44c2cb6937c5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_NetTransfersToParentSpecialPayment_08c3c33d-24d4-48c1-8a29-2f4756edae1f" xlink:href="ftre-20240331.xsd#ftre_NetTransfersToParentSpecialPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_ftre_NetTransfersToParentSpecialPayment_08c3c33d-24d4-48c1-8a29-2f4756edae1f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_NetTransfersFromToParentExcludingSpecialPayment_ef06f560-0f10-4c0e-95a0-459755ff96e0" xlink:href="ftre-20240331.xsd#ftre_NetTransfersFromToParentExcludingSpecialPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_ftre_NetTransfersFromToParentExcludingSpecialPayment_ef06f560-0f10-4c0e-95a0-459755ff96e0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AdjustmentsToAdditionalPaidInCapitalFormerParentInvestmentReclassification_5b051d03-9243-4f0d-acbe-6dd5bb566ac7" xlink:href="ftre-20240331.xsd#ftre_AdjustmentsToAdditionalPaidInCapitalFormerParentInvestmentReclassification"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_ftre_AdjustmentsToAdditionalPaidInCapitalFormerParentInvestmentReclassification_5b051d03-9243-4f0d-acbe-6dd5bb566ac7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_0c590471-f13c-4004-b93a-581d87f4e09c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_0c590471-f13c-4004-b93a-581d87f4e09c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_bdda537d-60ec-4a06-bc91-dee24df2d4dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_bdda537d-60ec-4a06-bc91-dee24df2d4dd" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_7ec890fb-52d0-4fac-8246-76ba9814cf43" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_17fd26ef-2f2b-4417-b406-7605b4a83a7d" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_7ec890fb-52d0-4fac-8246-76ba9814cf43" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_3873b2ee-0d8e-4e16-a1a7-debe45c6a22a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1d4cf616-7d31-40eb-a58f-948ea64ae18b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofCashFlowDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofCashFlowDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/IMMATERIALFINANCIALRESTATEMENTANDRECLASSIFICATIONSTOPRIORPERIODFINANCIALSTATEMENTSStatementsofCashFlowDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_fea2f40d-5992-4710-a35d-6ab349720235" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_9df3bf06-2285-4896-bc76-1a37c028498a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_fea2f40d-5992-4710-a35d-6ab349720235" xlink:to="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_9df3bf06-2285-4896-bc76-1a37c028498a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_b30521dd-3c91-4c9d-b230-9be9e643067b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_9df3bf06-2285-4896-bc76-1a37c028498a" xlink:to="loc_srt_RestatementAxis_b30521dd-3c91-4c9d-b230-9be9e643067b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_b30521dd-3c91-4c9d-b230-9be9e643067b_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_b30521dd-3c91-4c9d-b230-9be9e643067b" xlink:to="loc_srt_RestatementDomain_b30521dd-3c91-4c9d-b230-9be9e643067b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_a8ac2a19-3390-443e-a9af-1961e67bf27d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_b30521dd-3c91-4c9d-b230-9be9e643067b" xlink:to="loc_srt_RestatementDomain_a8ac2a19-3390-443e-a9af-1961e67bf27d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioPreviouslyReportedMember_caa5c37f-6554-4ea4-91d8-8af9f61be357" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioPreviouslyReportedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_a8ac2a19-3390-443e-a9af-1961e67bf27d" xlink:to="loc_srt_ScenarioPreviouslyReportedMember_caa5c37f-6554-4ea4-91d8-8af9f61be357" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_b8fdfaba-8bde-4121-a87a-9aa9b087a1be" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_a8ac2a19-3390-443e-a9af-1961e67bf27d" xlink:to="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_b8fdfaba-8bde-4121-a87a-9aa9b087a1be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_AsRestatedBeforeReclassificationAdjustmentsMember_0cc44e20-d4d7-46e1-9540-79c847829145" xlink:href="ftre-20240331.xsd#ftre_AsRestatedBeforeReclassificationAdjustmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_a8ac2a19-3390-443e-a9af-1961e67bf27d" xlink:to="loc_ftre_AsRestatedBeforeReclassificationAdjustmentsMember_0cc44e20-d4d7-46e1-9540-79c847829145" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_154c1d22-fd46-427a-a466-0d730bd0f273" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_fea2f40d-5992-4710-a35d-6ab349720235" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_154c1d22-fd46-427a-a466-0d730bd0f273" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_5070c62c-e4f8-4669-99a3-9db6222e4ee4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_154c1d22-fd46-427a-a466-0d730bd0f273" xlink:to="loc_us-gaap_NetIncomeLoss_5070c62c-e4f8-4669-99a3-9db6222e4ee4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_154c1d22-fd46-427a-a466-0d730bd0f273" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_f50e6840-9830-425a-9773-da92d08233ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_f50e6840-9830-425a-9773-da92d08233ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_d6d1f87c-dd1b-4704-a611-f011ee67c9dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:to="loc_us-gaap_ShareBasedCompensation_d6d1f87c-dd1b-4704-a611-f011ee67c9dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_e447c59d-44c1-47ec-b8d9-9cc65426b235" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_e447c59d-44c1-47ec-b8d9-9cc65426b235" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetImpairment_ed4abdb4-8323-4f56-a7dd-dc0f659c1a20" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GoodwillAndIntangibleAssetImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:to="loc_us-gaap_GoodwillAndIntangibleAssetImpairment_ed4abdb4-8323-4f56-a7dd-dc0f659c1a20" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_91e06893-a2cc-40a0-8ec7-2e3a15474eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_91e06893-a2cc-40a0-8ec7-2e3a15474eaf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_5da409ff-af9f-4913-83c5-31f1ff63d24c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNoncashIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_5da409ff-af9f-4913-83c5-31f1ff63d24c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e0c48b7a-7d82-4bd3-bba6-b630342ca00d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_f443881a-3a10-4cda-9ae8-662bcbd5b43b" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e0c48b7a-7d82-4bd3-bba6-b630342ca00d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_IncreaseDecreaseInAccountsReceivableAndContractWithCustomerAsset_eb26a34f-ed39-40d1-b860-5d1cab2f4317" xlink:href="ftre-20240331.xsd#ftre_IncreaseDecreaseInAccountsReceivableAndContractWithCustomerAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e0c48b7a-7d82-4bd3-bba6-b630342ca00d" xlink:to="loc_ftre_IncreaseDecreaseInAccountsReceivableAndContractWithCustomerAsset_eb26a34f-ed39-40d1-b860-5d1cab2f4317" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_2edcedeb-cab2-4a77-9447-884fe2937a25" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e0c48b7a-7d82-4bd3-bba6-b630342ca00d" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_2edcedeb-cab2-4a77-9447-884fe2937a25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_9187d065-5799-46be-9eec-3da7e2dc77d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e0c48b7a-7d82-4bd3-bba6-b630342ca00d" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_9187d065-5799-46be-9eec-3da7e2dc77d5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_887b2fb7-ce0e-4cda-98dc-8ff0ec71afbb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e0c48b7a-7d82-4bd3-bba6-b630342ca00d" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_887b2fb7-ce0e-4cda-98dc-8ff0ec71afbb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_74856b3b-b6c6-4926-b354-426f9602a6c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e0c48b7a-7d82-4bd3-bba6-b630342ca00d" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_74856b3b-b6c6-4926-b354-426f9602a6c8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1e27bb95-1bbc-4a09-b3bf-54f1c3774923" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_154c1d22-fd46-427a-a466-0d730bd0f273" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1e27bb95-1bbc-4a09-b3bf-54f1c3774923" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_c736078c-fe37-4bda-a066-2fe53ae90d09" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_fea2f40d-5992-4710-a35d-6ab349720235" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_c736078c-fe37-4bda-a066-2fe53ae90d09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireProductiveAssets_c16cbcd5-ee2e-4637-828d-33f2f1b24c35" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireProductiveAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_c736078c-fe37-4bda-a066-2fe53ae90d09" xlink:to="loc_us-gaap_PaymentsToAcquireProductiveAssets_c16cbcd5-ee2e-4637-828d-33f2f1b24c35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfProductiveAssets_b7299e7c-f403-4355-b7dd-6f31dd9bb597" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromSaleOfProductiveAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_c736078c-fe37-4bda-a066-2fe53ae90d09" xlink:to="loc_us-gaap_ProceedsFromSaleOfProductiveAssets_b7299e7c-f403-4355-b7dd-6f31dd9bb597" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_62f303bd-c14d-4de0-a43a-6e9d7fe9aca1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_c736078c-fe37-4bda-a066-2fe53ae90d09" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_62f303bd-c14d-4de0-a43a-6e9d7fe9aca1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_fea2f40d-5992-4710-a35d-6ab349720235" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_f1c033e0-2128-4a36-a482-5ddbbebe0ab6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_f1c033e0-2128-4a36-a482-5ddbbebe0ab6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_ae43dd44-e644-460a-870a-ba2c4e2e08ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_ae43dd44-e644-460a-870a-ba2c4e2e08ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_cc2df001-3beb-4b3e-9633-d2a7859ba019" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfSecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_cc2df001-3beb-4b3e-9633-d2a7859ba019" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt_7cef2fa2-91cc-4168-9e54-d2283f542a41" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt_7cef2fa2-91cc-4168-9e54-d2283f542a41" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_a56fcf67-4b53-4a15-bdcb-881d9f3bbb5e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_a56fcf67-4b53-4a15-bdcb-881d9f3bbb5e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_1fbddb46-ac54-4207-8f83-409eb648a04f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_1fbddb46-ac54-4207-8f83-409eb648a04f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_SpecialPaymentToFormerParent_a30d7a6e-d008-4669-9d9d-e30add00a77b" xlink:href="ftre-20240331.xsd#ftre_SpecialPaymentToFormerParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_ftre_SpecialPaymentToFormerParent_a30d7a6e-d008-4669-9d9d-e30add00a77b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ProceedsFromPaymentsToFormerParentCompany_e0473061-1d70-416d-acce-cd9a3358f456" xlink:href="ftre-20240331.xsd#ftre_ProceedsFromPaymentsToFormerParentCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_ftre_ProceedsFromPaymentsToFormerParentCompany_e0473061-1d70-416d-acce-cd9a3358f456" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_1d6cc2d9-80f1-45dc-a4a1-900d4695143b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c942bd96-3f66-4b92-9602-a8e9b1231d72" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_1d6cc2d9-80f1-45dc-a4a1-900d4695143b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_4653032c-91b8-423d-b91a-46df5511c90e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_fea2f40d-5992-4710-a35d-6ab349720235" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_4653032c-91b8-423d-b91a-46df5511c90e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_23c6629d-7853-4a8a-8df7-e9dce6323dab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_fea2f40d-5992-4710-a35d-6ab349720235" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_23c6629d-7853-4a8a-8df7-e9dce6323dab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_0b312300-5436-4df9-91e7-5daceadd2bf4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_fea2f40d-5992-4710-a35d-6ab349720235" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_0b312300-5436-4df9-91e7-5daceadd2bf4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_7e2f70a5-9b85-4733-a2e4-23f696df106a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fortrea.com/role/SUBSEQUENTEVENTSDetails" xlink:type="simple" xlink:href="ftre-20240331.xsd#SUBSEQUENTEVENTSDetails"/>
  <link:definitionLink xlink:role="http://www.fortrea.com/role/SUBSEQUENTEVENTSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_9d621c4a-a1b7-4a8a-8463-6eea4bde9983" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_0333e6b8-1215-422a-ad9d-16ede62679d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_9d621c4a-a1b7-4a8a-8463-6eea4bde9983" xlink:to="loc_us-gaap_SubsequentEventTable_0333e6b8-1215-422a-ad9d-16ede62679d7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_5af5af27-58d7-410e-8064-de59c137390b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_0333e6b8-1215-422a-ad9d-16ede62679d7" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_5af5af27-58d7-410e-8064-de59c137390b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_5af5af27-58d7-410e-8064-de59c137390b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_5af5af27-58d7-410e-8064-de59c137390b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_5af5af27-58d7-410e-8064-de59c137390b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_c350d9c3-23ee-44d7-a198-b497af143a00" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_5af5af27-58d7-410e-8064-de59c137390b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_c350d9c3-23ee-44d7-a198-b497af143a00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_ccbcffa4-e7db-4fc5-b174-d8347524ae34" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_c350d9c3-23ee-44d7-a198-b497af143a00" xlink:to="loc_us-gaap_SubsequentEventMember_ccbcffa4-e7db-4fc5-b174-d8347524ae34" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_4fe08e1f-f332-4b2e-89c9-e7c7d628ed9e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_0333e6b8-1215-422a-ad9d-16ede62679d7" xlink:to="loc_srt_StatementScenarioAxis_4fe08e1f-f332-4b2e-89c9-e7c7d628ed9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_4fe08e1f-f332-4b2e-89c9-e7c7d628ed9e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_4fe08e1f-f332-4b2e-89c9-e7c7d628ed9e" xlink:to="loc_srt_ScenarioUnspecifiedDomain_4fe08e1f-f332-4b2e-89c9-e7c7d628ed9e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_282152e9-d252-4fd9-9d5e-c4206d8bd7f2" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_4fe08e1f-f332-4b2e-89c9-e7c7d628ed9e" xlink:to="loc_srt_ScenarioUnspecifiedDomain_282152e9-d252-4fd9-9d5e-c4206d8bd7f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_2769467c-b78d-40b7-a057-8c2d7f7bea0f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_282152e9-d252-4fd9-9d5e-c4206d8bd7f2" xlink:to="loc_srt_ScenarioForecastMember_2769467c-b78d-40b7-a057-8c2d7f7bea0f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_69a03b0f-9d0e-4215-9564-628b594f950b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_0333e6b8-1215-422a-ad9d-16ede62679d7" xlink:to="loc_us-gaap_CreditFacilityAxis_69a03b0f-9d0e-4215-9564-628b594f950b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_69a03b0f-9d0e-4215-9564-628b594f950b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_69a03b0f-9d0e-4215-9564-628b594f950b" xlink:to="loc_us-gaap_CreditFacilityDomain_69a03b0f-9d0e-4215-9564-628b594f950b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_94f38482-c76f-4737-83e6-004673a8b6a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_69a03b0f-9d0e-4215-9564-628b594f950b" xlink:to="loc_us-gaap_CreditFacilityDomain_94f38482-c76f-4737-83e6-004673a8b6a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_52897461-2c0c-46f5-bb34-a5675be310d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_94f38482-c76f-4737-83e6-004673a8b6a3" xlink:to="loc_us-gaap_SecuredDebtMember_52897461-2c0c-46f5-bb34-a5675be310d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_fe1d496f-f25a-4757-ad2b-baa9dab4e86d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_0333e6b8-1215-422a-ad9d-16ede62679d7" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_fe1d496f-f25a-4757-ad2b-baa9dab4e86d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_fe1d496f-f25a-4757-ad2b-baa9dab4e86d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_fe1d496f-f25a-4757-ad2b-baa9dab4e86d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_fe1d496f-f25a-4757-ad2b-baa9dab4e86d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_baae48f0-4c9f-4833-a0d7-9b17005f0beb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_fe1d496f-f25a-4757-ad2b-baa9dab4e86d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_baae48f0-4c9f-4833-a0d7-9b17005f0beb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_bacfaf40-3b73-48cb-888d-4c8f853ca950" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_baae48f0-4c9f-4833-a0d7-9b17005f0beb" xlink:to="loc_us-gaap_LineOfCreditMember_bacfaf40-3b73-48cb-888d-4c8f853ca950" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_ReceivableSecuritizationTerm_4c06c99a-df35-4aa4-8357-6fccc0ef65a9" xlink:href="ftre-20240331.xsd#ftre_ReceivableSecuritizationTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_9d621c4a-a1b7-4a8a-8463-6eea4bde9983" xlink:to="loc_ftre_ReceivableSecuritizationTerm_4c06c99a-df35-4aa4-8357-6fccc0ef65a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableFromSecuritization_b35e32d8-30e4-439e-bfad-6102195517c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableFromSecuritization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_9d621c4a-a1b7-4a8a-8463-6eea4bde9983" xlink:to="loc_us-gaap_AccountsReceivableFromSecuritization_b35e32d8-30e4-439e-bfad-6102195517c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RatioOfIndebtednessToNetCapital1_9996d69f-922b-4c1f-b3c1-1a46694f12fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RatioOfIndebtednessToNetCapital1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_9d621c4a-a1b7-4a8a-8463-6eea4bde9983" xlink:to="loc_us-gaap_RatioOfIndebtednessToNetCapital1_9996d69f-922b-4c1f-b3c1-1a46694f12fd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ftre_DebtInstrumentInterestCoverageRatio_fd2abdc8-e560-4242-8d2b-3d558e702100" xlink:href="ftre-20240331.xsd#ftre_DebtInstrumentInterestCoverageRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_9d621c4a-a1b7-4a8a-8463-6eea4bde9983" xlink:to="loc_ftre_DebtInstrumentInterestCoverageRatio_fd2abdc8-e560-4242-8d2b-3d558e702100" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_PerformanceSharesMember" xlink:type="arc" order="5"/>
  </link:definitionLink>
</link:linkbase>
