Rotation

A rotation in the plane is a movement in a circular motion (a turn) through some angle that leaves shape unchanged and in which exactly one point (the centre of rotation) does not move i.e. a rotation in the plane has one invariant point. A rotation of a three-dimensional figure in space has a line of invariant points called the axis of rotation.

Rotation, like translation and reflection, is called an isometric transformation since it does not change the shape of the figure being rotated.