epicycle Hear it!

epicycle Definition

epi·cy·cle (ep′ə sī′kəl)

noun

  1. a circle whose center moves along the circumference of another, larger circle: term used to describe planetary motions in the Ptolemaic system
  2. Geom. a circle which generates a hypocycloid or epicycloid by rolling around the circumference of a fixed circle

Etymology: ME epicicle < LL epicyclus < Gr epikyklos < epi-, upon + kyklos, a circle: see cycle

epicycle Related Forms
ep′i·cy′·clic (-sīk′lik) adjective or ep′i·cy′·cli·cal
epicycle Usage Examples

Converse of object

  • use: One such feature was epicycles used to explain the apparent backward motion of planets across the sky.

Modifies a noun

  • theory: In the epicycle theory the Earth is in the center of a circle which has smaller circles rotating round its circumference.