Elastic and Plastic Bodies:

A body (such as a stretched rubber band and a loaded spring) which returns to its original (shape or size) state after the removal of the deforming force is called perfectly elastic. Therefore, if we go on increasing the strength of the external (deforming) force, a condition comes while the body no longer regains its original state. This deforming force features the elastic limit of the body. Instead if a body does not completely attain its original shape and size even on removing the deforming force, it is known as to be perfectly plastic.

In physics, elasticity stands for opposition to change. Therefore, steel is more elastic than rubber because steel offers more resistance to any effort to deform it. You must note that this meaning of the term elasticity is quite opposite to its meaning in common use (wherein we say that rubber is more elastic than steel).

The elasticity of a material is described in terms of stress and strain. You will learn it now.