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 helps engineers understand how materials will behave under different loads, ensuring safety and performance in structures. Materials typically exhibit linear behavior at low stress levels, following Hooke's Law, where stress is proportional to strain. As stress increases, materials may reach their yield point, leading to permanent deformation. Understanding these relationships is crucial in fields like civil engineering and materials science for designing safe and effective structures.