Epitrochoid vs. Epitrochoidal

Epitrochoid and Epitrochoidal Definitions
Epitrochoid
A geometric curve traced by a fixed point on one circle which rotates around the perimeter of another circle. Examples include the shape of the Wankel engine Category:en:Curves
Epitrochoidal
Being or relating to an epitrochoid.
Epitrochoid
A kind of curve. See Epicycloid, any Trochoid.