Octagon vs Decagon - What's the difference?

As nouns the difference between octagon and decagon

is that octagon is octagon while decagon is decagon.

(en noun)

(geometry) A polygon with eight sides and eight angles.

(martial arts, usually capitalized) The arena for mixed martial arts, particularly as trademarked by the .

(wikipedia decagon)

(en noun)

(geometry) A polygon with ten sides and ten angles.