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Webster 1913 Edition


Epicycle

Ep′i-cyˊcle

,
Noun.
[L.
epicyclus
, Gr. [GREEK];
ἐπί
upon + [GREEK] circle. See
Cycle
.]
1.
(Ptolemaic Astron.)
A circle, whose center moves round in the circumference of a greater circle; or a small circle, whose center, being fixed in the deferent of a planet, is carried along with the deferent, and yet, by its own peculiar motion, carries the body of the planet fastened to it round its proper center.
The schoolmen were like astronomers which did feign eccentrics, and
epicycles
, and such engines of orbs.
Bacon.
2.
(Mech.)
A circle which rolls on the circumference of another circle, either externally or internally.

Webster 1828 Edition


Epicycle

EP'ICYCLE

,
Noun.
[Gr. a circle.] A little circle, whose center is in the circumference of a greater circle; or a small orb, which, being fixed in the deferent of a planet, is carried along with it, and yet by its own peculiar motion, carries the body of the planet fastened to it round its proper center.

Definition 2024


epicycle

epicycle

See also: épicycle

English

Noun

epicycle (plural epicycles)

  1. (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.
  2. (mathematics) Any circle whose circumference rolls around that of another circle, thus creating a hypocycloid or epicycloid.

Derived terms

Translations