- a circle whose center moves along the circumference of another, larger circle: term used to describe planetary motions in the Ptolemaic system
- Geom. a circle which generates a hypocycloid or epicycloid by rolling around the circumference of a fixed circle
Origin of epicycleMiddle English epicicle from Late Latin epicyclus from Classical Greek epikyklos from epi-, upon + kyklos, a circle: see cycle
- In Ptolemaic cosmology, a small circle, the center of which moves on the circumference of a larger circle at whose center is the earth and the circumference of which describes the orbit of one of the planets around the earth.
- Mathematics A circle whose circumference rolls along the circumference of a fixed circle, thereby generating an epicycloid or a hypocycloid.
Origin of epicycleMiddle English epicicle from Late Latin epicyclus from Greek epikuklos epi- epi- kuklos circle ; see kwel-1 in Indo-European roots.
- (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.
- (mathematics) Any circle whose circumference rolls around that of another circle, thus creating a hypocycloid or epicycloid.
OriginSee also: épicycle
From Latin epicyclus, from Ancient Greek ἐπίκυκλος (epikuklos), from ἐπί (epi, “upon”) + κύκλος (kuklos, “circle”).