When any object of certain material is subjected to tensile or compressive or shear force, there may be a chance that its dimension will be affected.
If the dimension of a material is changed due to application of forces we can say that the material is under stress or experiencing the state of stress.
Stress is defined as the Force per unit cross section area.
Stress = F/A
Stress is mainly of two types normal stress and shear stress.
When the force applied is perpendicular to the cross section of the object then the stress is known as normal stress. (The force can be tensile or compressive)
When the force applied is parallel to the material cross section then the stress is known as shear stress.