Mechanical deformation refers to the change in shape or size of a material when subjected to an external force. This process can occur in various materials, including metals, plastics, and ceramics. Deformation can be elastic, where the material returns to its original shape after the force is removed, or plastic, where the change is permanent. The study of mechanical deformation is crucial in fields like engineering and materials science. Understanding how materials deform helps in designing structures and products that can withstand forces without failing. Common examples include bending a metal rod or stretching a rubber band.