A rotation is
a transformation which moves points so that they stay the same distance
from a fixed point, the center of rotation. The points are all turned
through the same angle about the center and appear to move along
arcs of concentric circles.
A rotation is, a rigid body movement
which keeps a point fixed. A rotation in three-dimensional space
keeps an entire line broken, i.e. a rotation in three-dimensional
space is a rotation around an orbit.
A rotation is defined when its center, the angle of rotation, and
the direction of the turn are given. An anti-clockwise turn is said
to be positive and a clockwise turn is negative.
