An octagon has eight vertices. An octagon is a shape with eight sides, which makes eight angles and, therefore, eight vertices.
All octagons have eight sides made of straight lines, but only regular octagons have sides that are all equal, like a stop sign. Irregular octagons can even be concave, with some angles pointing inward. However, no side can cross another side in an octagon or in any type of polygon. An octagon is a type of polygon, as a polygon is an enclosed shape with straight lines for sides. Triangles, squares and rectangles are also polygons, as are hexagons. Circles, however, are not polygons.