Normal Stress, 

a)   gives the intensity of stress uniformly distributed over the cross section in an axially loaded, prismatic bar of arbitrary cross-sectional shape.

i) Axial force P acts through the centroid of the cross-sectional area

ii) Uniform stress condition  exists throughout the length of the bar except near the ends

c) Stresses act in a direction perpendicular to the cut surface, they are called normal stresses.

d) Tensile stresses as positive and compressive stresses as negative.