When an external deforming force is applied on any elastic body, it Due to inter molecular force of attraction, a restoring force is produced in the body opposite to the external force to retain its form intact. The magnitude of the restoring force produced in per unit area of the body is called stress.
Let a force of magnitude F is applied on a body of area A. The stress of the body is, P= F/A
The stress is a scalar quantity.
The dimension of stress is [P] = [ML-1T-2]
Unit of stress is Nm-2 or Pascal (Pa)