I. ˈkärdēˌȯid noun
( -s )
Etymology: cardi- + -oid
: a heart-shaped closed curve traced by a point on the circumference of a circle as it rolls completely around an equal fixed circle and forms an epicycloid of one cusp and one loop, the polar equation with cusp as pole being r=a (1 - cos θ ), where a is the diameter of either circle
[s]cardioid.jpg[/s] [
cardioid: ABP fixed circle; PCD first position of rolling circle; P tracing point; PM diameter through P; P 1 , P 2 , P 3 , P 4 various positions of P; P 1 M 1 , P 2 M 2 , P 3 M 3 , P 4 M 4 various positions of PM
]
II. adjective
: connected with or relating to a cardioid