A polygon is any closed figure with three or more straight sides. "Closed" means that there are no gaping holes in it and that all sides connect together.

These Are Polygons:

These Are Not Polygons:

That's right, a circle is not a polygon. It doesn't have all the properties, and it's really hard to count the number of sides.

Names of Some Common Polygons

Important Vocabulary

Polygons have a lot of important vocabulary terms that come with them. You will need to memorize these, but don't worry, they aren't too difficult.

• Angle: the shape formed when two rays meet at a common point. AKA "the corner."
• Vertex: the point where two rays meet; the corner point of a polygon. The plural of vertex is vertices. 
• Side: the straight edge of a polygon.

• Equiangular: a figure where all angles are equal in measure.
• Equilateral: a figure where all sides are equal in length.
• Regular Polygon: an equilateral, equiangular polygon. 

Regular Polygons

You're probably familiar with these shapes

These Are Not Regular

Base and Height of a Polygon

• Base: the bottom side of a polygon.
• Height: the height of a polygon is the perpendicular distance from the top-most vertex to the base. The height and base ALWAYS form a right angle.

Polygons Practice: