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 in American English
(ˈkɑrdiˌɔɪd)
noun
Ancient Mathematics
a curve more or less in the shape of a heart, traced by a point on the circumference of a circle that rolls around the circumference of another equal circle
Word origin
Gr kardioeidēs, heart-shaped < kardia, heart + -oeidēs, -oid