Define angular speed and angular velocity.

(N/A) Angular speed is defined as the rate of change of angular displacement with respect to time. It is a scalar quantity. If an object rotates by an angle $\Delta \theta$ in time $\Delta t$,the average angular speed is $\omega_{avg} = \frac{\Delta \theta}{\Delta t}$. The instantaneous angular speed is $\omega = \lim_{\Delta t \to 0} \frac{\Delta \theta}{\Delta t} = \frac{d\theta}{dt}$.
Angular velocity is defined as the rate of change of angular displacement vector with respect to time. It is a vector quantity,denoted by $\vec{\omega}$. Its direction is given by the right-hand rule,perpendicular to the plane of rotation. The instantaneous angular velocity is $\vec{\omega} = \frac{d\vec{\theta}}{dt}$.