What makes an octagon an octagon?

Answer 1

The term octagon means an eight sided geometrical figure. It has to have eight sides. If it has only six sides it's a hexagon. If it has three sides it's a triangle.

Answer 2

An octagon is a polygon with eight sides and eight angles. All eight sides of an octagon are equal in length, and all eight angles are equal, measuring 135 degrees. These properties define the shape of an octagon and distinguish it from other polygons.