Epicycle
noun ·Rare ·Advanced level
Definitions
- 1 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.
"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 a circle that rolls around (inside or outside) another circle; generates an epicycloid or hypocycloid wordnet
- 3 Any circle whose circumference rolls around that of another circle, thus creating a hypocycloid or epicycloid.
- 4 A ring of atoms joining parts of an already cyclic compound
- 5 An ad hoc complication added to a model to make it fit the known data figuratively
"If two chronicles seemed contradictory, instead of trying to choose between them, a rationalization (epicycle) was devised to cover both."
Example
More examples"The epicycle made it possible for the Greeks to explain the planetary movements."
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.
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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.