A simple closed figure formed of three or more linesegments is called a polygon. The linesegments which form a polygon are called its sides.
The point at which two adjacent sides of a polygon meet is called a vertex of the polygon. The plural of vertex is vertices.
Types of polygons
A polygon with three sides is called a triangle.
A polygon with four sides is called a quadrilateral.
A polygon with five sides is called a pentagon.
A polygon with six sides is called a hexagon.
A polygon with seven sides is called a heptagon.
A polygon with eight sides is called an octagon and so on.