In order to completely represent an angular displacement, by a vector, it must fix the following three conditions :

**1. Direction of the axis of rotation.**

It is fixed by drawing a line perpendicular to the plane of rotation, in which the angular displacement takes place. In other words, it is fixed along the axis of rotation.

**2. Magnitude of angular displacement.**

It is fixed by the length of the vector drawn along the axis of rotation, to some suitable scale.

**3. Sense of the angular displacement.**

It is fixed by a right hand screw rule. This rule states that if a screw rotates in a fixed nut in a clockwise direction, i.e. if the angular displacement is clockwise and an observer is looking along the axis of rotation, then the arrow head will point away from the observer. Similarly, if the angular displacement is anti-clockwise, then the arrow head will point towards the observer.