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epicycle

 - 2 dictionary results

ep⋅i⋅cy⋅cle

[ep-uh-sahy-kuhl]
–noun
1. Astronomy. a small circle the center of which moves around in the circumference of a larger circle: used in Ptolemaic astronomy to account for observed periodic irregularities in planetary motions.
2. Mathematics. a circle that rolls, externally or internally, without slipping, on another circle, generating an epicycloid or hypocycloid.

Origin:
1350–1400; ME < MF < LL epicyclus < Gk epíkyklos. See epi-, cycle


ep⋅i⋅cy⋅clic [ep-uh-sahy-klik, -sik-lik] , adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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ep·i·cy·cle   (ěp'ĭ-sī'kəl)   
n.  
  1. 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.

  2. Mathematics A circle whose circumference rolls along the circumference of a fixed circle, thereby generating an epicycloid or a hypocycloid.


[Middle English epicicle, from Late Latin epicyclus, from Greek epikuklos : epi-, epi- + kuklos, circle; see kwel-1 in Indo-European roots.]
ep'i·cy'clic (-sī'klĭk, -sĭk'lĭk) adj.
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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