The amount of deformation compared to the original size is known as?

Strain is defined as the measure of deformation representing the displacement between particles in a material body. It is calculated as the change in length divided by the original length, effectively quantifying how much a material deforms relative to its original size. This concept is critical in engineering, as it helps predict how materials will respond under various forces and loads. Understanding strain is essential for ensuring that structures and components can withstand operational stresses without failing.

Other options, while related to material properties, address different concepts. Hooke's Law pertains to the proportional relationship between stress and strain for elastic materials but does not define the measure of deformation itself. The yield point refers to the level of stress at which a material begins to deform plastically, meaning it won't return to its original shape, and ultimate strength is the maximum stress a material can withstand before failure. Each of these terms is vital in understanding material behavior, but strain specifically refers to the ratio of deformation to original dimensions.