Hexagon.
The vertices are the "points" of a polygon.
19. sides=vertices
diagonal
A polygon with nine vertices also has nine sides, and is therefore a "nonagon".
A polygon with three vertices and three sides is a triangle. A polygon with four vertices and four sides is a quadrilateral.
A tetrahedron, assuming the four vertices are not coplanar.
Hexagon.
There is no polygon with this name.
It is a quadrilateral.
HEXAGON
Just think
A quadrilateral is a polygon with four sides and four vertices.
A polygon is a closed figure bounded by sides only. Triangle is the polygon of 3 sides and 3 vertices.
pentogon
The vertices are the "points" of a polygon.
No .. parallelograms are quadrilaterals. A quadrilateral is any polygon with four sides and four vertices.