There are three types of body are mainly considered in strength of material.
1) Elastic body
A body regains its originals dimensions when the external load acting on it is completely removed are called as elastic body.
2) Plastic body
A body which gets permanently defored under the action of load and not coming back to its original dimensions on removal of load is called as plastic body.
3) Rigid body
A body which does not undergo any change in its dimension under the action of external load as rigid body. No body is perfectly rigid.