epicycle

[ ep-uh-sahy-kuhl ]

/ ˈɛp əˌsaɪ kəl /

noun

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.

Mathematics. a circle that rolls, externally or internally, without slipping, on another circle, generating an epicycloid or hypocycloid.

Origin of epicycle

1350–1400; Middle English <Middle French <Late Latin epicyclus<Greek epíkyklos.See epi-, cycle

OTHER WORDS FROM epicycle

ep·i·cy·clic

[ep-uh-sahy-klik, -sik-lik], /ˌɛp əˈsaɪ klɪk, -ˈsɪk lɪk/, adjective

Words nearby epicycle

epicure, epicurean, Epicureanism, Epicurus, epicuticle, epicycle, epicyclic train, epicycloid, epicycloidal gear, epicycloidal wheel, epicystitis

Dictionary.com UnabridgedBased on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for epicycle

The small circle carried by a bigger one was called an Epicycle.
Pioneers of Science|Oliver Lodge
The moon moves on an epicycle centred on a second epicycle, itself centred on a deferent, excentric to the earth.
History of Astronomy|George Forbes
An epicycle in addition to the hypocycle was introduced into Mercury's orbit.
The Life of Galileo Galilei, with Illustrations of the Advancement of Experimental Philosophy|John Elliot Drinkwater Bethune
The planet is supposed to move equably in the epicycle, and to be carried by the Sun unequably in the proportion of the distances.
The Life of Galileo Galilei, with Illustrations of the Advancement of Experimental Philosophy|John Elliot Drinkwater Bethune

To help out of this difficulty, the worst possible mechanical scheme was invented, that known as the epicycle.
Astronomy|David Todd

British Dictionary definitions for epicycle

epicycle

/ (ˈɛpɪˌsaɪkəl) /

noun

astronomy (in the Ptolemaic system) a small circle, around which a planet was thought to revolve, whose centre describes a larger circle (the deferent) centred on the earth

a circle that rolls around the inside or outside of another circle, so generating an epicycloid or hypocycloid

Derived forms of epicycle

epicyclic (ˌɛpɪˈsaɪklɪk, -ˈsɪklɪk) or epicyclical, adjective

Word Origin for epicycle

C14: from Late Latin epicyclus, from Greek epikuklos; see epi-, cycle

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for epicycle

epicycle

[ ĕp′ĭ-sī′kəl ]

In Ptolemaic cosmology, a small circle representing a temporary adjustment to the position of a planet as it orbits the Earth. The five known planets, along with the Sun and Moon, were conceived as moving through the sky in large circular paths with the Earth at their center. As a planet moved along its path, it occasionally departed from its regular motion to follow a much smaller circle centered on the orbital path itself. These smaller circles, or epicycles, were necessary to reconcile the observed motions of the planets with a geocentric model of the universe. The epicycles of the inferior planets Mercury and Venus were fixed to the orbit of the Sun and explained why those planets were never observed far from it in the sky. The epicycles of the superior planets Mars, Jupiter, and Saturn explained why those bodies were sometimes observed to move backward in their orbits, a phenomenon known as retrograde motion and explained in a heliocentric model by the differing orbital velocities of the Earth and the planet being observed. See illustration at Ptolemaic system.

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

单词	epicycle
释义	epicycle [ ep-uh-sahy-kuhl ] / ˈɛp əˌsaɪ kəl / noun 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. Mathematics. a circle that rolls, externally or internally, without slipping, on another circle, generating an epicycloid or hypocycloid. Origin of epicycle 1350–1400; Middle English <Middle French <Late Latin epicyclus<Greek epíkyklos.See epi-, cycle OTHER WORDS FROM epicycle ep·i·cy·clic [ep-uh-sahy-klik, -sik-lik], /ˌɛp əˈsaɪ klɪk, -ˈsɪk lɪk/, adjective Words nearby epicycle epicure, epicurean, Epicureanism, Epicurus, epicuticle, epicycle, epicyclic train, epicycloid, epicycloidal gear, epicycloidal wheel, epicystitis Dictionary.com UnabridgedBased on the Random House Unabridged Dictionary, © Random House, Inc. 2020 Example sentences from the Web for epicycle The small circle carried by a bigger one was called an Epicycle. Pioneers of Science\|Oliver Lodge The moon moves on an epicycle centred on a second epicycle, itself centred on a deferent, excentric to the earth. History of Astronomy\|George Forbes An epicycle in addition to the hypocycle was introduced into Mercury's orbit. The Life of Galileo Galilei, with Illustrations of the Advancement of Experimental Philosophy\|John Elliot Drinkwater Bethune The planet is supposed to move equably in the epicycle, and to be carried by the Sun unequably in the proportion of the distances. The Life of Galileo Galilei, with Illustrations of the Advancement of Experimental Philosophy\|John Elliot Drinkwater Bethune To help out of this difficulty, the worst possible mechanical scheme was invented, that known as the epicycle. Astronomy\|David Todd British Dictionary definitions for epicycle epicycle / (ˈɛpɪˌsaɪkəl) / noun astronomy (in the Ptolemaic system) a small circle, around which a planet was thought to revolve, whose centre describes a larger circle (the deferent) centred on the earth a circle that rolls around the inside or outside of another circle, so generating an epicycloid or hypocycloid Derived forms of epicycle epicyclic (ˌɛpɪˈsaɪklɪk, -ˈsɪklɪk) or epicyclical, adjective Word Origin for epicycle C14: from Late Latin epicyclus, from Greek epikuklos; see epi-, cycle Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Scientific definitions for epicycle epicycle [ ĕp′ĭ-sī′kəl ] In Ptolemaic cosmology, a small circle representing a temporary adjustment to the position of a planet as it orbits the Earth. The five known planets, along with the Sun and Moon, were conceived as moving through the sky in large circular paths with the Earth at their center. As a planet moved along its path, it occasionally departed from its regular motion to follow a much smaller circle centered on the orbital path itself. These smaller circles, or epicycles, were necessary to reconcile the observed motions of the planets with a geocentric model of the universe. The epicycles of the inferior planets Mercury and Venus were fixed to the orbit of the Sun and explained why those planets were never observed far from it in the sky. The epicycles of the superior planets Mars, Jupiter, and Saturn explained why those bodies were sometimes observed to move backward in their orbits, a phenomenon known as retrograde motion and explained in a heliocentric model by the differing orbital velocities of the Earth and the planet being observed. See illustration at Ptolemaic system. A circle whose circumference rolls along the circumference of a fixed circle, thereby generating an epicycloid or a hypocycloid. The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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