A famous scientist Robert Brown observed that molecule substance moved in zigzag path. Their motion is random. They collide with each other and move in a new direction after collision in zigzag fashion. This type of motion present in the molecules of matter is called “Brownian motion”.
The property of solid by virtue of which a solid body recovers its original shape after the removal of an applied force is called Elasticity.
If applied force on a solid is gradually increased, a state is reached after which the material will not return to its original shape even after the removal of applied force.
This limit is called Elastic Limit. After elastic limit, material is permanently deformed. Different substances have different elastic limit.