= Mechanical strength
<Mechanical strength> describes the <stress> a material withstands before a specified limiting event, such as yielding or fracture. The event, loading mode and test conditions must be stated: tensile strength, compressive strength and yield strength measure different responses.
In a simple tension test, engineering <stress> is applied <force> divided by initial cross-sectional area, $\sigma=F/A_0$. A specimen carrying $10\,\mathrm{kN}$ over $100\,\mathrm{mm}^2$ experiences $100\,\mathrm{MPa}$ by that convention. Strength is distinct from <Young's modulus>, which relates tensile stress to elastic strain, and from <fracture toughness>, which concerns resistance to crack growth. <Microstructure>, defects, <temperature> and loading history can all influence the measured limit.
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