In case of elastic deformations, a building experiences deformations as force is applied and returning to its original shape when removed. However, extreme earthquake forces may generate inelastic deformations in which the element does not return to its original shape after the force is removed. Ductility is the property of certain elements that have inelastic deformation before failing. Building elements constructed with ductile materials have a "reserve capacity" to resist earthquake overloads. Therefore, buildings constructed of ductile elements, such as steel and adequately reinforced concrete, tend to withstand earthquakes much better than those constructed of brittle materials such as unreinforced masonry.