If the angular velocity of the body performing rotatory motion is non-uniform, then the body is said to possess angular acceleration.

The rate of change of angular velocity is called angular acceleration.

If the angular velocity of a body moving in a circular path changes from ω_{1} to ω_{2} in time t then its angular acceleration is

**α = dω/dt = d/dt(dθ/dt) = d ^{2}θ/dt^{2} = (ω_{2} – ω_{1})/t**

The angular acceleration is measured in terms of rad s^{-2} and its dimensional formula is T^{-2}.