A moon or a man-made body in orbit around a planet: For clarity, natural satellites are commonly described as "moons" to distinguish them from man-made or artificial satellites.

Relay station in space for sending telephone, television, telex, and other messages around the world: Most communications satellites are in geostationary orbit, appearing to hang fixed over one point on the Earth's surface.

Messages are sent to and from the satellites via ground stations.

The four largest moons, or satellites, of Jupiter, specifically Ganymede, Callisto, Io, and Europa. The Galilean satellites were first observed by Galileo Galilei.