apsis
noun
ap·sis ˈap-səs 
plural apsides ˈap-sə-ˌdēz
1
: the point in an astronomical orbit at which the distance of the body from the center of attraction is either greatest or least
2
: apse sense 2
Example Sentences
Recent Examples on the Web Each term is sometimes called an apsis, which refers to the nearest or farthest point between a celestial body and its host. 
NBC News, 5 Jan. 2022
NBC News, 5 Jan. 2022 Word History
Etymology
borrowed from Medieval Latin apsīs, apsīda "arc, vault," going back to Latin apsīd-, apsīs (also hapsīs, absīs) "arc described by a planet, segment of a circle," borrowed from Greek hapsīd-, hapsís (Ionic apsís) "loop, mesh, rim of a wheel, wheel, disk, segment cut off by a rainbow, arch, vault," from ap-s-, stem in noun derivation of háptein "to fasten," háptesthai "to fasten oneself to, grasp" + -īd-, -īs, noun suffix — more at haptics
First Known Use
1601, in the meaning defined at sense 1