👉 Stiffness is a property of materials that refers to their resistance to change in shape under stress. In physics and engineering, stiffness can be defined as the amount of force required to deform an object by changing its length or width, without causing significant deformation. The concept of stiffness arises from the observation that when a material has large forces applied to it, it tends to expand rather than contract, which is why materials like steel tend to have high stiffness. This property is also known as elastic resistance,