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In [[astronomy]], an [[apsis]] (plural ''apsides'') is either of the two points in an [[orbit]] at which the orbiting body makes its closest or farthest approach to the primary.<ref>"[http://en.wiktionary.org/wiki/apsis Entry for 'Apsis']." ''[http://en.wiktionary.org/wiki/Wiktionary:Main_Page Wiktionary]. Accessed January 16, 2008.</ref><ref>Dooling, Dave, and Kneale, Ruth A., eds. "[http://www.nso.edu/press/glossary.html#apsis Entry for 'Apsis']," ''Glossary of Terms'', National Solar Observatory, February 21, 2005. Accessed January 16, 2008.</ref>

In [[astronomy]], an [[apsis]] (plural ''apsides'') is either of the two points in an [[orbit]] at which the orbiting body makes its closest or farthest approach to the primary.<ref>"[http://en.wiktionary.org/wiki/apsis Entry for 'Apsis']." ''[http://en.wiktionary.org/wiki/Wiktionary:Main_Page Wiktionary]''. Accessed January 16, 2008.</ref><ref>Dooling, Dave, and Kneale, Ruth A., eds. "[http://www.nso.edu/press/glossary.html#apsis Entry for 'Apsis']," ''Glossary of Terms'', National Solar Observatory, February 21, 2005. Accessed January 16, 2008.</ref>

The point of closest approach is called the ''periapsis'' (from the Greek ''peri'' around).

The point of closest approach is called the ''periapsis'' (from the Greek ''peri'' around).