- Astronomy. either of two points in an eccentric orbit, one (higher apsis) farthest from the center of attraction, the other (lower apsis) nearest to the center of attraction.
- Architecture. an apse.
Origin of apsis
1595–1605; < Latin < Greek hapsís (felloe of) a wheel, arch, vault, orig., fastening, equivalent to háp(tein) to fasten + -sis -sis
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Examples from the Web for apsides
The two are joined by a diameter called the line of the apsides.The Sailor's Word-Book
William Henry Smyth
The line of apsides of a large proportion of comets will be approximately coincident with the solar orbit.Comets and Meteors
The “line of apsides” is that which joins them, forming the major axis of the orbit.
This point was called "the excentric," and the line from the excentric to the Earth was called "the line of apsides."The Science of the Stars
E. Walter Maunder
The line of the apsides of the moon's orbit revolves from west to east, through her whole course, in about nine years.Letters on Astronomy
- Also called: apse either of two points lying at the extremities of an eccentric orbit of a planet, satellite, etc, such as the aphelion and perihelion of a planet or the apogee and perigee of the moon. The line of apsides connects two such points and is the principal axis of the orbit
- another name for apse (def. 1)
C17: via Latin from Greek; see apse
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for apsides
"perigree of the moon, perihelion of a planet" (plural apsides), 1650s, from Latin apsis "arch, vault" (see apse).
Online Etymology Dictionary, © 2010 Douglas Harper
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.