Strength of materials is an engineering discipline concerned with the mechanical behavior of solid objects subjected to forces. It involves analyzing how various materials respond to applied loads, calculating internal stresses, and determining failure criteria. Key concepts include stress, defined as the internal force per unit area, and strain, which measures the deformation relative to the original dimensions. The relationship between stress and strain often defines the material's response, distinguishing between elastic behavior, where deformation is temporary, and plastic behavior, where permanent deformation occurs. The field examines fundamental properties such as Young's modulus, shear modulus, and Poisson's ratio, allowing engineers to predict structural integrity and optimize material selection for applications ranging from civil structures to aerospace components.