Some quantities are especially related to elasticity which is discussed below:
(a) Perfectly elastic body: A body that returns to its original shape and size on the removal of the deforming force (when deformed within elastic limit) is called the elastic body. If a body recovers its original shape and size as soon the deforming force is withdrawn, the body is called a perfectly elastic body.
(b) Plastic body: In physics, plasticity describes the deformation of a (solid) material undergoing non-reversible changes of shape in response to applied forces. If a body retains its changed shape and size after the removal of the deforming force then that body is called the plastic body. The property of the body is called plasticity. Sometimes, this type of body is called the inelastic body.
(c) Perfectly rigid body: A rigid body is a solid body in which deformation is zero or so small it can be neglected. A body is called perfectly rigid if it does not suffer any train under the action of the defocusing force. Nobody is the perfectly rigid body. However, glass is approximately perfectly rigid.
