Epicycle

Pronunciation

• UK IPA: /ˈɛpɪsaɪkÉ™l/

Origin

From Latin epicyclus, from Ancient Greek ἐπίκυκλος, from ἐπί ("upon") + κύκλος ("circle").

Full definition of epicycle

Noun

1. (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.
• 1603, John Florio, translating Michel de Montaigne, Essays, 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.
2. (mathematics) Any circle whose circumference rolls around that of another circle, thus creating a hypocycloid or epicycloid.

Derived terms

• epicyclic