\begin{definition}[Definition:Rotation (Geometry)/Axis]
Let $r_\theta$ be a rotation in the Euclidean Space $\Gamma = \R^n$.
The set $A$ of points in $\Gamma$ such that:
:$\forall P \in A: \map {r_\theta} P = P$
is called the '''axis of rotation''' of $r_\theta$.
\end{definition}