<Li> Non-convex: a line may be found which meets its boundary more than twice . Equivalently, there exists a line segment between two boundary points that passes outside the polygon . </Li> <Li> Simple: the boundary of the polygon does not cross itself . All convex polygons are simple . </Li> <Li> Concave . Non-convex and simple . There is at least one interior angle greater than 180 ° . </Li> <Li> Star - shaped: the whole interior is visible from at least one point, without crossing any edge . The polygon must be simple, and may be convex or concave . </Li>

A polygon in which one or more interior angle has a measure greater than 180