Elasticity:

Elasticity is an inherent property by virtue of which a body undergoing a change in length, volume, or shape due to the application of external forces, tends to regain its original length, volume, or shape as soon as the external forces are withdrawn.

Bodies that can regain their original conditions completely on withdrawal of the deforming forces are said to be perfectly elastic, on the other hand, the bodies which don’t show any tendency to regain their original condition after the withdrawal of deforming forces are said to be perfectly plastic.

‘Quartz fibre’ is the nearest approach to a perfectly elastic body. Putty is an example of a perfectly plastic body.