The path of a ray of light passing through a glass prism is shown below.

In this diagram, the angle of prism, angle of incidence, angle of emergence and angle of deviation, respectively, have been represented by 

 

The angle between two refracting surfaces of prism is called angle of prism. The angle between incident ray to normal is called angle of incidence. The angle between emergent ray to normal is called angle of emergent. The angle between corresponding  incident ray to corresponding emergent is called angle of emergent.