epicycle

== English == === Etymology === From Latin epicyclus, from Ancient Greek ἐπίκυκλος (epíkuklos), from ἐπί (epí, “upon”) + κύκλος (kúklos, “circle”). The ad hoc complication sense is a generalization from the archetype supplied by the Ptolemaic astronomy sense. === Pronunciation === (UK) IPA(key): /ˈɛpɪˌsaɪkəl/ === Noun === epicycle (plural epicycles) (astronomy) A small circle whose centre is on the circumference of a larger circle; in Ptolemaic astronomy it was seen as the basis of revolution of the "seven planets", given a fixed central Earth. Coordinate term: deferent , Folio Society, 2006, vol.1, p.155: Is it not [Philosophie], that […] teacheth miserie, famine and sicknesse to laugh? Not by reason of some imaginarie Epicicles, but by naturall and palpable reasons. (geometry) Any circle whose circumference rolls around that of another circle, thus creating a hypocycloid or epicycloid. (organic chemistry) A ring of atoms joining parts of an already cyclic compound (figuratively) An ad hoc complication added to a model to make it fit the known data ==== Derived terms ==== epicyclic (adjective) ==== Translations ==== ==== See also ==== (ad hoc complication):