- (n.) In a curve referred to polar coordinates, any point for which the radius vector is a maximum or minimum.
- (n.) 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.
- (n.) Same as Apse.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). apsis. Retrieved September 21, 2026, from http://smartdefine.org/apsis/definitions/1975329 |
| Chicago | Webster's. 2011. "apsis" http://smartdefine.org/apsis/definitions/1975329 (accessed September 21, 2026). |
| Harvard | Webster's 2011, apsis, Smart Define, viewed 21 September, 2026, <http://smartdefine.org/apsis/definitions/1975329>. |
| MLA | Webster's. "apsis" 27 May 2011. Web. 21 September 2026. <http://smartdefine.org/apsis/definitions/1975329> |