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cardioid

[kahr-dee-oid]
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noun Mathematics.
  1. a somewhat heart-shaped curve, being the path of a point on a circle that rolls externally, without slipping, on another equal circle. Equation: r = a(1−cosA).

Origin of cardioid

First recorded in 1745–55, cardioid is from the Greek word kardioeidḗs heart-shaped. See cardi-, -oid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for cardioid

cardioid

noun
  1. a heart-shaped curve generated by a fixed point on a circle as it rolls around another fixed circle of equal radius, a. Equation: r = a (1 – cos φ), where r is the radius vector and φ is the polar angle
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

cardioid in Science

cardioid

[kärdē-oid′]
  1. A heart-shaped plane curve, the locus of a fixed point on a circle that rolls on the circumference of another circle with the same radius.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.