Editing Apsis (section)

===Etymology===
The words ''perihelion'' and ''aphelion'' were coined by [[Johannes Kepler]]<ref>Klein, Ernest, ''A Comprehensive Etymological Dictionary of the English Language'', Elsevier, Amsterdam, 1965.  ([https://archive.org/stream/AComprehensiveEtymologicalDictionaryOfTheEnglishLanguageByErnestKlein/A%20Comprehensive%20Etymological%20Dictionary%20of%20the%20English%20Language%20by%20Ernest%20Klein_djvu.txt Archived version])</ref> to describe the orbital motions of the planets around the Sun.
The words are formed from the prefixes ''peri-'' (Greek: ''περί'', near)  and ''apo-'' (Greek: ''ἀπό'', away from), affixed to the Greek word for the Sun, (''ἥλιος'', or ''hēlíos'').<ref name=Sun/>

Various related terms are used for other [[Celestial body|celestial objects]]. The suffixes ''-gee'', ''-helion'', ''-astron'' and ''-galacticon'' are frequently used in the astronomical literature when referring to the Earth, Sun, stars, and the [[Galactic Center]] respectively.  The suffix ''-jove'' is occasionally used for Jupiter, but ''-saturnium'' has very rarely been used in the last 50 years for Saturn. The ''-gee'' form is also used as a generic closest-approach-to "any planet" term—instead of applying it only to Earth.

During the [[Apollo program]], the terms ''pericynthion'' and ''apocynthion'' were used when referring to [[lunar orbit|orbiting the Moon]];  they reference Cynthia, an alternative name for the Greek Moon goddess [[Artemis]].<ref>{{cite web | title = Apollo 15 Mission Report | work = Glossary | url = https://history.nasa.gov/alsj/a15/a15mr-f.htm | access-date = October 16, 2009 | archive-date = March 19, 2010 | archive-url = https://web.archive.org/web/20100319081116/http://history.nasa.gov/alsj/a15/a15mr-f.htm | url-status = live }}</ref> More recently, during the [[Artemis program]], the terms ''perilune'' and ''apolune'' have been used.<ref>{{cite conference |author=R. Dendy |author2=D. Zeleznikar |author3=M. Zemba | title = NASA Lunar Exploration – Gateway's Power and Propulsion Element Communications Links | conference = 38th International Communications Satellite Systems Conference (ICSSC) | date = September 27, 2021 | location = Arlington, VA | url = https://ntrs.nasa.gov/citations/20210019019 | access-date = July 18, 2022 | archive-date = Mar 29, 2022 | archive-url=https://web.archive.org/web/20220329140256/https://ntrs.nasa.gov/citations/20210019019 | url-status = live }}</ref>

Regarding black holes, the term peribothron was first used in a 1976 paper by J. Frank and M. J. Rees,<ref>{{cite journal |author1=Frank, J. |author2=Rees, M.J. |title=Effects of massive black holes on dense stellar systems. |journal=MNRAS |volume=176 |pages=633–646 |date=September 1, 1976 |issue=6908 |doi=10.1093/mnras/176.3.633|bibcode=1976MNRAS.176..633F|doi-access=free }}</ref> who credit W. R. Stoeger for suggesting creating a term using the greek word for pit: "bothron".

The terms ''perimelasma'' and ''apomelasma'' (from a Greek root) were used by physicist and science-fiction author [[Geoffrey A. Landis]] in a story published in 1998,<ref name="Asimov's">[http://www.infinityplus.co.uk/stories/perimelasma.htm ''Perimelasma''] {{Webarchive|url=https://web.archive.org/web/20190225210759/http://www.infinityplus.co.uk/stories/perimelasma.htm |date=February 25, 2019 }}, by Geoffrey Landis, first published in ''[[Asimov's Science Fiction]]'', January 1998, republished at ''[[Infinity Plus]]''</ref> thus appearing before ''perinigricon'' and ''aponigricon'' (from Latin) in the scientific literature in 2002.<ref>{{cite journal |author=R. Schödel |author2=T. Ott |author3=R. Genzel |author4=R. Hofmann |author5=M. Lehnert |author6=A. Eckart |author7=N. Mouawad |author8=T. Alexander |author9=M. J. Reid |author10=R. Lenzen |author11=M. Hartung |author12=F. Lacombe |author13=D. Rouan |author14=E. Gendron |author15=G. Rousset |author16=A.-M. Lagrange |author17=W. Brandner |author18=N. Ageorges |author19=C. Lidman |author20=A. F. M. Moorwood |author21=J. Spyromilio |author22=N. Hubin |author23=K. M. Menten |title=A star in a 15.2-year orbit around the supermassive black hole at the centre of the Milky Way |journal=Nature |volume=419 |pages=694–696 |date=October 17, 2002 |issue=6908 |doi=10.1038/nature01121|arxiv=astro-ph/0210426 |bibcode=2002Natur.419..694S |pmid=12384690|s2cid=4302128 }}</ref>