For an object moving in an elliptical orbit about another celestial body, the point of closest approach is called the periapsis (from the Greek

*peri*= near). At this point in the orbit, the object is travelling at its greatest speed (Kepler's Second Law).The periapsis is equivalent to the:

- Perihelion: for a celestial body orbiting the Sun.
- Perigee: for a celestial body (in particular the Moon or artificial satellites) orbiting the Earth.
- Periastron: for a celestial body orbiting a star (e.g. in a binary star system).

The point of maximum distance in the orbit is called the apoapsis.