What's the difference between epicycloid and epicycloidal?

Epicycloid

Definition:

• (n.) A curve traced by a point in the circumference of a circle which rolls on the convex side of a fixed circle.

Example Sentences:

• (1) Therefore, the paths of the individual mandibular points are epicycloids or hypocycloids.

Epicycloidal

Definition:

• (a.) Pertaining to the epicycloid, or having its properties.

Example Sentences:

• (1) Therefore, the paths of the individual mandibular points are epicycloids or hypocycloids.