The paper discusses the decoupling limit of the CP-conserving two-Higgs-doublet model (2HDM), where the lightest Higgs boson has Standard-Model-like couplings. In this limit, the properties of the lightest Higgs boson are nearly indistinguishable from those of the Standard Model Higgs boson. The first nontrivial corrections to Higgs couplings in the approach to the decoupling limit are evaluated. The importance of detecting such deviations in precision Higgs measurements at future colliders is emphasized. The paper also clarifies the case in which a neutral Higgs boson can possess Standard-Model-like couplings in a regime where the decoupling limit does not apply. The two-Higgs-doublet sector of the minimal supersymmetric model illustrates many of the above features. The paper begins by introducing the CP-conserving 2HDM, which contains two complex Higgs doublets. The scalar potential is defined, and the conditions for the scalar potential to be bounded from below are derived. The scalar fields develop non-zero vacuum expectation values, leading to the physical Higgs bosons: two CP-even scalars (h and H), one CP-odd scalar (A), and a charged Higgs pair (H±). The squared-mass parameters of these Higgs bosons are derived, and the mixing angle between the CP-even Higgs bosons is determined. The decoupling limit is defined as the case where the mass of the lightest Higgs boson is significantly smaller than the masses of the other Higgs bosons. In this limit, the properties of the lightest Higgs boson coincide with those of the Standard Model Higgs boson. The paper discusses the implications of this limit for Higgs couplings to gauge bosons, fermions, and other Higgs bosons. It also considers the case where the Higgs couplings to fermions are approximately the same as those of the Standard Model Higgs boson, even outside the decoupling limit. The paper also discusses the impact of radiative corrections on the decoupling limit and the possibility of a Standard Model-like Higgs boson in a parameter regime where all Higgs masses are in the range of the electroweak scale. The paper concludes by emphasizing the importance of the decoupling limit in understanding the behavior of the 2HDM and its implications for future Higgs measurements.The paper discusses the decoupling limit of the CP-conserving two-Higgs-doublet model (2HDM), where the lightest Higgs boson has Standard-Model-like couplings. In this limit, the properties of the lightest Higgs boson are nearly indistinguishable from those of the Standard Model Higgs boson. The first nontrivial corrections to Higgs couplings in the approach to the decoupling limit are evaluated. The importance of detecting such deviations in precision Higgs measurements at future colliders is emphasized. The paper also clarifies the case in which a neutral Higgs boson can possess Standard-Model-like couplings in a regime where the decoupling limit does not apply. The two-Higgs-doublet sector of the minimal supersymmetric model illustrates many of the above features. The paper begins by introducing the CP-conserving 2HDM, which contains two complex Higgs doublets. The scalar potential is defined, and the conditions for the scalar potential to be bounded from below are derived. The scalar fields develop non-zero vacuum expectation values, leading to the physical Higgs bosons: two CP-even scalars (h and H), one CP-odd scalar (A), and a charged Higgs pair (H±). The squared-mass parameters of these Higgs bosons are derived, and the mixing angle between the CP-even Higgs bosons is determined. The decoupling limit is defined as the case where the mass of the lightest Higgs boson is significantly smaller than the masses of the other Higgs bosons. In this limit, the properties of the lightest Higgs boson coincide with those of the Standard Model Higgs boson. The paper discusses the implications of this limit for Higgs couplings to gauge bosons, fermions, and other Higgs bosons. It also considers the case where the Higgs couplings to fermions are approximately the same as those of the Standard Model Higgs boson, even outside the decoupling limit. The paper also discusses the impact of radiative corrections on the decoupling limit and the possibility of a Standard Model-like Higgs boson in a parameter regime where all Higgs masses are in the range of the electroweak scale. The paper concludes by emphasizing the importance of the decoupling limit in understanding the behavior of the 2HDM and its implications for future Higgs measurements.