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Related to cycloid: prolate cycloid, hypocycloid
click for a larger image
top: surface view of cycloid scales of a bony fish
bottom: The parametric equations of this cycloid are
x = r(θ - sin θ),
y = r(1 - cos θ).
click for a larger image


1. Resembling a circle.
2. Zoology
a. Relating to or being a kind of fish scale that is thin, rounded, and smooth-edged and often shows concentric growth rings.
b. Having cycloid scales.
3. Psychology Afflicted with or relating to cyclothymia.
n. Mathematics
The curve traced by a point on the circumference of a circle that rolls on a straight line.

[French cycloïde, from Greek kukloeidēs, circular : kuklos, circle; see kwel- in Indo-European roots + -oeidēs, -oid.]

cy·cloi′dal (-kloid′l) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


1. (Mathematics) resembling a circle
2. (Zoology) (of fish scales) rounded, thin, and smooth-edged, as those of the salmon
3. (Psychiatry) psychiatry (of a type of personality) characterized by exaggerated swings of mood between elation and depression. See also cyclothymia
4. (Mathematics) geometry the curve described by a point on the circumference of a circle as the circle rolls along a straight line. Compare trochoid1
5. (Zoology) a fish that has cycloid scales
cyˈcloidal adj
cyˈcloidally adv
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈsaɪ klɔɪd)

1. resembling a circle; circular.
a. (of the scale of a fish) smooth-edged and more or less circular in form.
b. (of a fish) having such scales.
3. Psychiatry. of or denoting a personality type characterized by wide fluctuations in mood within the normal range.
4. a curve generated by a point on the circumference of a circle that rolls, without slipping, on a straight line.
[1655–65; < Greek kykloeidḗs like a circle. See cycle, -oid]
cy•cloi′dal, adj.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.cycloid - a line generated by a point on a circle rolling along a straight linecycloid - a line generated by a point on a circle rolling along a straight line
line roulette, roulette - a line generated by a point on one figure rolling around a second figure
curate cycloid - a cycloid generated by a point inside the rolling circle
prolate cycloid - a cycloid generated by a point outside the rolling circle
Adj.1.cycloid - resembling a circle
rounded - curving and somewhat round in shape rather than jagged; "low rounded hills"; "rounded shoulders"
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.


[ˈsaɪklɔɪd] n (Geom) → cicloide f
Collins Italian Dictionary 1st Edition © HarperCollins Publishers 1995
References in classic literature ?
It was in the left hand try-pot of the Pequod, with the soapstone diligently circling round me, that I was first indirectly struck by the remarkable fact, that in geometry all bodies gliding along the cycloid, my soapstone for example, will descend from any point in precisely the same time.
In the first course, there was a shoulder of mutton cut into an equilateral triangle, a piece of beef into a rhomboides, and a pudding into a cycloid. The second course was two ducks trussed up in the form of fiddles; sausages and puddings resembling flutes and hautboys, and a breast of veal in the shape of a harp.
In brief - distinct grounds, and vivid circular or cycloid figures, of no meaning, are here Median laws.
The section on Size and Shape concludes by introducing the helix and the cycloid. As these figures are best understood as traced out by a moving point, Lockhart uses them to segue into the second section of the book, Time and Space.
However, the spin cycloid averages out the macroscopic magnetization.
It also provided a kind of microscale preview of Cycloid V, 2017-18, and Ekpyrotic String VI, 2016-17, a pair of enormous looping forms that wrapped themselves like wild amusement-park slides around two of the gallery's pillars.
For more details about the solution of problem and animated cycloid curve [19] see Figure 1.
Leonhard [24] described menstrual exacerbations in some patients with catatonic symptoms diagnosed with cycloid psychoses, but did not describe menstrual exacerbation in periodic catatonia.
The tape synthesis identifies 4 useful mechanism structures of the geared linkages with linear actuation and parallel connected chain and classifies them in two types: planetary geared linkages (Asi) and cycloid geared linkages (Zsi).
In anisotropic tissues, to overcome this difficulty, methodological procedures have been proposed such as the 'orientator' sampling (Mattfeldt et al., 1990), or the so-called 'vertical sections' analyzed with 'cycloid arcs' (see figure 5D) (Baddeley et al., 1986).