septangular

例句：

1. 1.The octagon is a shape with eight sides.
   八边形是一种有八个边的图形。
2. 2.The octagon is the shape of an inverted triangle.
   八边形是倒三角形的形状。
3. 3.The octagon is used to represent the shape of a star.
   八边形用来表示星星的形状。