Compressive strain refers to the deformation that occurs when a material is subjected to compressive forces, which push the material together. This strain is measured as the change in length of the material divided by its original length. When a material experiences compressive strain, it typically shortens and becomes denser. In engineering and materials science, understanding compressive strain is crucial for designing structures like buildings and bridges. Materials such as concrete and steel are often evaluated for their compressive strength to ensure they can withstand the forces they will encounter during use.