Prism :- Any transparent medium bounded by any number of surfaces such that the surface on which light is incident and the surface from which light emerges are plane and not parallel is called a prism.
Angle of prism/Refracting angle of prism
The angle between the faces on which light is incident and from which light emerges is called angle of prism. In the above figures it is shown by angle A.
Angle of deviation(δ)
The angle through which the light ray bends after passing through a prism or the angle between incident ray and emergent ray is called angle of deviation.