Octagon is a polygon in geometry, which has 8 sides and 8 angles. That means the number of vertices is 8 and the number of edges is 8. All the sides are joint with each other end-to-end to form a shape. These sides are in a straight line form, they are not curved or disjoint with each other. Each interior angle of a regular polygon is 135°, therefore, the measure of exterior angle becomes 180° – 135° = 45°. The sum of the interior angles of the octagon is 135 × 8 = 1080°.