noun

epicycle

EP-ih-sy-kəl

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Epicycle (noun) means a small circle whose centre moves around the edge of a larger circle, used in the old Ptolemaic model of the solar system to explain planetary motion. Example: “In Ptolemaic astronomy, each planet was thought to move on an epicycle.”

noun

astronomy A small circle whose centre moves around the edge of a larger circle, used in the old Ptolemaic model of the solar system to explain planetary motion.

"In Ptolemaic astronomy, each planet was thought to move on an epicycle."

"The model used epicycles to account for the odd looping paths of planets in the sky."

"Ancient astronomers added epicycles to make their predictions match observations."

geometry A circle that rolls around the outside of another circle, tracing a curved path called an epicycloid.

"Mathematicians study the curve traced by a point on an epicycle as it rolls."

"An epicycle rolling around a fixed circle produces a looping curve."

"The size of the epicycle determines the shape of the resulting epicycloid."

How to use epicycle

Learner’s notes

In plain EnglishA small circle that moves around the edge of a bigger one, especially in old models of planetary motion.

When to use it

It is a specialist term from the history of astronomy and geometry, not everyday vocabulary.

Memory tip

Picture a circle riding on the rim of a bigger circle - that image is the core of the word in both astronomy and geometry.

Trace the full origin ↓

Common pairings

epicycles and deferents add an epicycle model with epicycles

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C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

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Fill the gap

Can you complete this real example?

In Ptolemaic astronomy, each planet was thought to move on an _____.

Etymology

Epicycle comes from Latin epicyclus, which itself derives from Greek epikuklos, formed from epi, meaning upon, and kuklos, meaning circle.

Origin: Latin

Rhymes for epicycle

cycle bicycle recycle unicycle tricycle motorcycle

See all rhymes for epicycle →

Frequently asked questions

What is an epicycle in astronomy?

It is a small circle whose centre travels around a bigger circle, used in the old Earth-centred model of the universe to explain how planets appeared to move.

Why did ancient astronomers use epicycles?

They added epicycles to make their predictions of planetary positions match what was actually observed in the sky.

Does epicycle only refer to astronomy?

No, in geometry it also describes a circle rolling around another circle, tracing a curve called an epicycloid.

What is the meaning of epicycle?

"epicycle" (noun) means a small circle whose centre moves around the edge of a larger circle, used in the old Ptolemaic model of the solar system to explain planetary motion.