Either of the two points in planetary orbits where they are at the greatest and the least distance from the sun, and are termed higher or lower accordingly. The two are joined by a diameter called the line of the apsides.
apsis, v. absis. ...
A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.
·noun ·same·as <<Apse>>. II. Apsis ·noun In a curve referred to polar coordinates, any point for wh...
Webster's Dictionary of the English Language