Question

define angular displacement, angular velocity and angular acceleration

Answer 1

angular displacement is defined as the angle through which an object moves on a circular path. It is theangle, in radians, between the initial and final positions. (θf - θi) = angular displacement. θ = s/r.
rate of change of angular position of a rotating body.is known as angular velocity
Angular acceleration is the rate of change of angular velocity. In SI units, it is measured in radians per second squared, and is usually denoted by the Greek letter alpha. 

Answer 2

the rate of change of displacement in a circular path is known as angular displacement and the rate of change of angular displacement is known as angular velocity and the rate of change of angular velocity is known as angular acceleration