An octagon is any closed shape with eight straight sides. In a regular octagon, unlike an irregular octagon, all the sides are equal in length. Irregular octagons can look completely different from one another.
Each interior angle of a regular octagon measures 135 degrees. Each of its exterior angles measures 45 degrees. The properties of an irregular octagon differ in that the interior angles can have measurements that are greater or less than 135 degrees. Some may have interior angles greater than 180 degrees, in which case they are concave octagons, while others may have interior angles less than 180 degrees, making them convex octagons.