There are two types of stresses : 

Normal and Shear or tangential stress

(1) Normal stress : Here the force is applied normal to the surface. 

It is again of two types : Longitudinal and Bulk or volume stress. 

(i) Longitudinal stress 

(a) Deforming force is applied parallel to the length and causes increase in length.

(b) Area taken for calculation of stress is area of cross section. 

(c) Longitudinal stress produced due to increase in length of a body under a deforming force is called tensile stress. 

(d) Longitudinal stress produced due to decrease in length of a body under a deforming force is called compressional stress. 

(ii) Bulk or Volume stress 

(a) It occurs in solids, liquids or gases. 

(b) Deforming force is applied normal to surface at all points. 

(c) It is equal to change in pressure because change in pressure is responsible for change in volume. 

(2) Shear or tangential stress : It comes in picture when successive layers of solid move on each other i.e., when there is a relative displacement between various layers of solid. 

(i) Here deforming force is applied tangential to one of the faces. 

(ii) Area for calculation is the area of the face on which force is applied. 

(iii) It produces change in shape, volume remaining the same.