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An Apsis is the point of closest or furthest approach for a body in an elliptical orbit from its center of attraction (or center of mass of the system). The periapsis is the point of closest approach and the apoapsis is the position of farthest extent for the orbit. A straight line drawn through the periapsis and apoapsis is the line of apsides.[1]

There are various terms related to celestial objects and their respective orbits:

Body Closest approach Farthest approach
Galaxy Perigalacticon Apogalacticon
Star Periastron Apastron
Black hole Perimelasma/Perinigricon Apomelasma/Aponigricon
Sun Perihelion Aphelion
Mercury Perihermion Apohermion
Venus Pericytherion/Pericytherean/Perikrition Apocytherion/Apocytherean/Apokrition
Earth Perigee Apogee
Moon Periselene/Pericynthion/Perilune Aposelene/Apocynthion/Apolune
Mars Periareion Apoareion
Jupiter Perizene/Perijove Apozene/Apojove
Saturn Perikrone/Perisaturnium Apokrone/Aposaturnium
Uranus Periuranion Apouranion
Neptune Periposeidion Apoposedion
Pluto Perihadion Apohadion