It's the other way around . . . a pentagon is one of many kinds of polygon. In fact, "Poly" actually means 'many'.
A Pentagon
A hexagon is a poloygon.
A nonagon.
A hexagon.
Heptagon or septagon
a poloygon that does not curve or cross and is closed
45
9
A square
square, rectangle, rhombus...
360 /each exterior angle
a regular shape which includes many sides possible but all sides are equeal in length