Well a triangle has 3 sides and vertices.
A line segment has endpoints
Any polygon is.
I believe it may be called a diagonal.
A diagonal
Any closed polygon could be made using the descriptions above.
Hexagon
Maybe line segment.
I am going to say a line segment. No segments is a line, and one endpoint is a ray.
A circle. has no endpoints.
A expample of a plane figure with 6 sides and 6 vertices is called a hexagon. hex means 6.
You will get a smaller pentagon and it will be inverted relative to the original.
Edge