Answer: A polygon is classified by how many sides it has.
Step-by-step explanation: Polygons are classified based on the number of sides that they have.
For example, if a polygon has 3 sides, it's classified as a triangle. If it has 4 sides, it's called a quadrilateral. If it has 5 sides, it's called a pentagon.
A list of polygons and their number of sides is attached in the image.