An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The line connecting the two apsides, i.e. the major axis of an elliptical orbit. → apsis.

Apsides, pl. of → apside; → line.

The point of greatest or least distance of the orbit of a celestial body from a center of attraction. The closest point is the → periapsis, the further point the → apoapsis.

L. apsis "arch, vault," from Gk. hapsis "loop, arch," from haptein "fasten together".

Mod.Pers. habâk "top of the head; the summit of a mountain".

Of an elliptical orbit, the straight line drawn from the → perigee to the → apogee.

→ line, → apsides.