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.
When two rays are joined at their endpoints, the resulting figure is called an angle. The point where the rays meet is known as the vertex, while the rays themselves are referred to as the sides of the angle. Angles can be measured in degrees to indicate their size.