Apsis is a derived term of periapsis.
In astronomy terms the difference between periapsis and apsis
is that periapsis is the point of a body's elliptical orbit about the system's centre of mass where the distance between the body and the centre of mass is at its minimum while apsis is either of the points in the elliptical orbit of a planet or comet where it is closest or furthest from the sun; perihelion or aphelion; an apside.
periapsis
English
Noun
(periapsides)
(astronomy) The point of a body's elliptical orbit about the system's centre of mass where the distance between the body and the centre of mass is at its minimum.
Usage notes
In the case of some particular celestial bodies, specialised terms are used.
Antonyms
* apoapsis
Synonyms
* pericenter
Related terms
* periastron
* perihelion
* perilune
* perigee
See also
* (Apsis)
apsis
Noun
(apsides)
(architecture) A recess or projection, with a dome or vault, at the east end of a church; an apse.
(astronomy) Either of the points in the elliptical orbit of a planet or comet where it is closest or furthest from the sun; perihelion or aphelion; an apside
Derived terms
* periapsis
* apoapsis