cycloid

[ sahy-kloid ]

adjective

resembling a circle; circular.
(of the scale of a fish) smooth-edged, more or less circular in form, and having concentric striations.

(of a fish) having such scales.
Psychiatry. of or noting a personality type characterized by wide fluctuation in mood within the normal range.

noun

a cycloid fish.
Geometry. a curve generated by a point on the circumference of a circle that rolls, without slipping, on a straight line.

Origin of cycloid

First recorded in 1655–65, cycloid is from the Greek word kykloeidḗs like a circle. See cycl-, -oid

Other words from cycloid

cy·cloi·dal, adjective
cy·cloi·dal·ly, adverb

Words Nearby cycloid

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use cycloid in a sentence

In brief—distinct grounds, and vivid circular or cycloid figures, of no meaning, are here Median laws.
The Works of Edgar Allan Poe | Edgar Allan Poe
In 1644 he published a tract on the properties of the cycloid in which he suggested a solution of the problem of its quadrature.
A History of Science, Volume 2(of 5) | Henry Smith Williams
Other sharks had piercing teeth (Cladoselache and Cladodus); some, the petalodonts, had peculiar cycloid cutting teeth.
Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3 | Various
The tail is diphycercal in all, ending in a long point, and the body is covered with cycloid scales.
A Guide to the Study of Fishes, Volume 1 (of 2) | David Starr Jordan
The Holoptychiidæ have the pectoral fins acute, the scales cycloid, enameled, and the teeth very complex.
A Guide to the Study of Fishes, Volume 1 (of 2) | David Starr Jordan

British Dictionary definitions for cycloid

cycloid

/ (ˈsaɪklɔɪd) /

adjective

resembling a circle
(of fish scales) rounded, thin, and smooth-edged, as those of the salmon

psychiatry (of a type of personality) characterized by exaggerated swings of mood between elation and depression: See also cyclothymia

noun

geometry the curve described by a point on the circumference of a circle as the circle rolls along a straight line: Compare trochoid (def. 1)
a fish that has cycloid scales

Derived forms of cycloid

cycloidal, adjective
cycloidally, adverb

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 cycloid

cycloid

[ sī′kloid′ ]

Resembling a circle.
Thin, rounded, and smooth-edged, like a disk. Used of fish scales.

The curve traced by a point on the circumference of a circle that rolls on a straight line.

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