Apsis

An apsis (Greek:ἁψίς; plural apsides /ˈæpsᵻdiːz/, Greek: ἁψίδες) is an extreme point in an object's orbit. The word comes via Latin from Greek and is cognate with apse. For elliptic orbits about a larger body, there are two apsides, named with the prefixes peri- (fromπερί (peri), meaning "near") and ap-, or apo- (fromἀπ(ό) (ap(ó)), meaning "away from") added to a reference to the thing being orbited.