How can strain be defined in the context of material science?

Strain in material science is defined as the ratio of the change in length of a material to its original length. This definition highlights how materials deform under stress. When a load is applied to a material, it typically undergoes dimensional changes, whether that be stretching, compressing, or bending. The strain quantifies this deformation by expressing it as a fraction or percentage of the original length before any load is applied.

For example, if a metal rod originally measures 100 cm in length and is stretched to 101 cm, the change in length is 1 cm. The strain would therefore be 1 cm divided by 100 cm, resulting in a strain of 0.01, or 1%. This dimensionless quantity is critical in understanding how materials react under various forces and is fundamental in engineering and physics to ensure that structures can withstand anticipated loads without failing.

The other choices focus on different aspects of material behavior that, while important, do not correctly define strain specifically.