cycloid

[ sahy-kloid ]

adjective

1. resembling a circle; circular.
2. (of the scale of a fish) smooth-edged, more or less circular in form, and having concentric striations.
3. (of a fish) having such scales.
4. Psychiatry. of or noting a personality type characterized by wide fluctuation in mood within the normal range.

noun

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

cycloid

/ ˈsaɪklɔɪd /

adjective

1. resembling a circle
2. (of fish scales) rounded, thin, and smooth-edged, as those of the salmon
3. psychiatry (of a type of personality) characterized by exaggerated swings of mood between elation and depression See also cyclothymia

noun

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

cycloid

/ sī′kloid′ /

1. Resembling a circle.
2. Thin, rounded, and smooth-edged, like a disk. Used of fish scales.
3. The curve traced by a point on the circumference of a circle that rolls on a straight line.

Derived Forms

• cyˈcloidal, adjective
• cyˈcloidally, adverb

Other Words From

• cy·cloidal adjective
• cy·cloidal·ly adverb

Word History and Origins

Origin of cycloid¹

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

Example Sentences

Kahn played with natural light in the Fort Worth building, suffused with skylights, reflectors and cycloid barrel vaults.

From New York Times

That curve, called a cycloid, is produced by a point on the circumference of a circle or wheel as it rolls along a straight line.

From New York Times

There are connections to be made between some of these displays — even the “Tracks of Galileo” with its allusion to “cycloids” and the rectangular-wheeled trike — that might have also been subtly explored.

From New York Times

This curve of quickest descent, as it is sometimes called, is, in a vacuum, the same as the cycloid.

From Project Gutenberg

It is impossible to mill out even a convex cycloid or epicycloid, by the means and in the manner above described.

From Project Gutenberg