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: 1745–55; < Greekkardioeidḗs heart-shaped. See cardi-, -oid
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
cardioid (kär'dē-oid') Pronunciation Key
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.