How is strain defined in materials science?

Strain in materials science is defined as the measure of deformation representing the displacement between particles in a material body. It is calculated as the change in length (or other dimensions) divided by the original length (or dimension), typically expressed as a dimensionless ratio or percentage.

The choice that identifies the measurable amount of load that displaces material is conceptually close, as it implies a relationship between the applied load and the resulting deformation. However, strain specifically describes how much a material deforms in response to that load relative to its original dimensions, rather than the load itself.

In contrast, the other options refer to aspects that are not appropriate definitions of strain. The original dimension of a material does not represent how the material deforms under load, the maximum stress a material can withstand pertains to its strength rather than deformation, and the residual strength of a deformed material speaks to its capacity after yielding, rather than defining the nature of strain itself. Thus, while the choice provided may relate to deformation, it does not encapsulate the precise definition of strain in the context of materials science.