Crossword Dictionary

What's The Definition Of Apsis?

\Ap"sis\ ([a^]p"s[i^]s), n.; pl. {Apsides} ([a^]p"s[i^]*d[=e]z). See {Apse}. [L. apsis, absis, Gr. "apsi`s, "apsi^dos, a tying, fastening, the hoop of a wheel, the wheel, a bow, arch, vault, fr. "a`ptein to fasten.] 1. (Astron.) One of the two points of an orbit, as of a planet or satellite, which are at the greatest and least distance from the central body, corresponding to the aphelion and perihelion of a planet, or to the apogee and perigee of the moon. The more distant is called the higher apsis; the other, the lower apsis; and the line joining them, the line of apsides. 2. (Math.) In a curve referred to polar co["o]rdinates, any point for which the radius vector is a maximum or minimum. 3. (Arch.) Same as {Apse}.