Which property describes a material's tendency to deform plastically under tensile stress, often measured as elongation?

• A. Ductility
• B. Elasticity
• C. Hardness
• D. Brittleness

Answer: (A)

Ductility is the property that describes how much a material can plastically deform under tensile load, and it’s often measured as elongation. In a tensile test, ductile materials stretch noticeably before breaking, showing a significant increase in length (percent elongation) and usually necking as the test progresses. This contrasts with elasticity, where deformation is reversible after removing the load; hardness, which measures resistance to surface indentation; and brittleness, where materials crack with very little plastic deformation and thus have low elongation. So the best answer captures the ability to undergo plastic, lasting deformation under tension, typically quantified by elongation.