What's the difference between enneagon and enneagonal?

Enneagon

---

Definition:

• (n.) A polygon or plane figure with nine sides and nine angles; a nonagon.

Example Sentences:

• (1) Hexagons and pentagons were found but no evidence of other polygons (up to enneagon) was obtained.

Enneagonal

---

Definition:

• (a.) Belonging to an enneagon; having nine angles.

Example Sentences:

• (1) Hexagons and pentagons were found but no evidence of other polygons (up to enneagon) was obtained.