Natural satellite

''Looking for the pool variant? See Moons (game).'' A moon is a celestial body that orbits a planet or smaller body, which is called the primary. It is, in more technical terms, a natural satellite.

The large gas giants of Sol have extensive systems of moons, including half a dozen comparable in size to Earth's moon: the four Galilean moons, Saturn's Titan, and Neptune's Triton. Saturn has an additional six mid-sized moons massive enough to have achieved hydrostatic equilibrium, and Uranus has five. Of the inner planets, Mercury and Venus have no moons at all; Earth has one large moon (Luna); and Mars has two tiny moons, Phobos and Deimos.