- The orbiting of one celestial body around another.
- A single complete course of such an orbit. For artificial satellites,
revolutions are figured relative to a given point on the planet's surface.
Because Earth is spinning west to east, a spacecraft in a west-to-east
orbit takes longer to complete one revolution than to complete one orbit
relative to a fixed point in space. For example, the Space Shuttle may
make 16 orbits of Earth in a day but only 15 revolutions.