Definition of "cycloid" [cy•cloid]

• Resembling a circle. (adjective)
• Zoology Thin, rounded, and smooth-edged; disklike. Used of fish scales. (adjective)
• Zoology Having or composed of such scales. (adjective)
• Psychiatry Afflicted with or relating to cyclothymia. (adjective)
• Mathematics The curve traced by a point on the circumference of a circle that rolls on a straight line. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "8.13 A Beautiful Curve ∗ One of the most wonderful curves I can think of, and one that had a great in fl uence on me in my youth, is called a cycloid, which is the locus ∗ ∗ of a fi xed point on the circumference of a circle as it rolls, without slipping, along a straight line (Figure 8.8)."
• "A cycloid is a curve traced by a point in the circumference of a wheel when the wheel is rolled along in a straight line."
• "Newton solved it correctly; he showed that the curve was a part of what is termed a cycloid -- that is to say, a curve like that which is described by a point on the rim of a carriage-wheel as the wheel runs along the ground."