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cy·cloid (sikloid′)
Share:
adj.
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.
[Frenchcycloïde, fromGreekkukloeides, circular : kuklos, circle; see kwel-1 in the Appendix of Indo-European roots + -oeides, -oid.]
cy·cloidal(-kloid′l)adj.
(click for a larger image)
cycloid
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)
cycloid
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
 

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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