# cycloid

[sahy-kloid]

- 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.

- 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^{}

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

## Examples from the Web for cycloid

### Historical Examples

#### It is not yet known to what philosopher we owe the invention of the cycloid.

Letters on EnglandVoltaire

#### Pascal is said to have written his treatise on the cycloid from a religious motive.

Sir Christopher Wren</p>Lucy Phillimore

#### So that it is a kind of Cycloid, of which, however, the points can be found geometrically.

Treatise on Light</p>Christiaan Huygens

#### Rather it travels along a cycloid, bending back upon itself, following the movement of man.

A Novelist on NovelsW. L. George

#### In brief—distinct grounds, and vivid circular or cycloid figures, of no meaning, are here Median laws.

The Works of Edgar Allan PoeEdgar Allan Poe

# cycloid

- 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 depressionSee also cyclothymia

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

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

# 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.

The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.