What term describes the deformation of a material under stress?

The term that describes the deformation of a material under stress is strain. Strain is a measure of how much a material deforms in response to the applied forces, specifically quantifying the change in shape or size relative to its original dimensions. This deformation occurs as materials experience stress, which is the internal force per unit area within the material caused by external loads.

Strain can be expressed as a ratio of the change in length to the original length, allowing engineers to evaluate how materials will perform under various loading conditions. This understanding is crucial in structural engineering, as it affects design decisions related to safety, stability, and performance of materials and structures under load.

In contrast, deformation refers to the overall change in shape or size, while compression specifically refers to a type of stress that causes materials to shorten. Deflection is the displacement of a structural element under load, often used in the context of beams. Fracture denotes the failure of a material leading to separation, which occurs after limits of strain are exceeded. Understanding strain helps civil engineers predict how structures will behave, ensuring they can design safe and resilient systems.