This document defines key terms related to stress, strain, and deformation of solids. It defines tensile stress and strain as stress and strain resulting from pulling forces that increase length. Compressive stress and strain are defined as stress and strain resulting from pushing forces that decrease length. Shear stress and strain result from tangential forces that cause shearing. Examples of ductile, brittle, and malleable materials are provided. Poisson's ratio relates lateral and linear strain. Hooke's law states stress is proportional to strain within a material's elastic limit. Other terms defined include modulus of elasticity, modulus of rigidity, bulk modulus, factor of safety, resilience, strain energy, and strain energy density.