Rotation

noun

1. The act of turning around a centre or an axis.

   "The earth's rotation about its axis is responsible for its being slightly oblate rather than a sphere."

2. A single complete cycle around a centre or an axis.

   "Earth's moon completes a rotation every twenty-seven days or so."

3. A regular variation in a sequence, such as to even-out wear, or people taking turns in a task; a duty roster.

   "In rotation, each member of the group would be responsible for the beacon fire."

4. An operation on a metric space that is a continuous isometry and fixes at least one point.

   "The function mapping (x,y) to (−y,x) is a rotation."

5. The set of starting pitchers of a team.