# Definition:Rotation (Geometry)/Angle

Let $r_\theta$ be a rotation in the Euclidean Space $\Gamma = \R^n$.
Let $\map {r_\theta} P = P'$ about a point $O$ on the axis of rotation of $r_\theta$.
The number $\theta$ which defines the angle $POP'$ is called the angle of rotation of $r_\theta$.