The "Stress-Strain Relationship" describes how materials deform under applied forces. Stress is the force applied per unit area, while strain measures the deformation resulting from that stress. This relationship is crucial in understanding how materials behave when subjected to loads, helping engineers design safe structures. In many materials, the relationship is linear within a certain range, known as the elastic region, where they return to their original shape after the load is removed. Beyond this point, materials may enter the plastic region, where permanent deformation occurs. Understanding this relationship is essential for predicting material performance in various applications.