This document defines and describes various mechanical properties of materials including elasticity, plasticity, rigidity, stress, strain, and Hooke's law. It then defines and gives equations for three types of stress (tensile, volume, and shear) and three types of strain (tensile, volume, and shear). Finally, it defines three elastic constants (Young's modulus, bulk modulus, and modulus of rigidity), Poisson's ratio, and provides the process for determining Young's modulus of the material of a wire.