A *polygon* is a closed shape with straight sides. Rectangles, triangles, hexagons, and octagons are all examples of *polygons*.

The word *polygon* comes from the Greeks, like most terms in geometry, which they invented. It simply means many (*poly*) angles (*gon*). A polygon canâ€™t have any curves or any gaps or openings in its shape. If you want to describe something as angular and closed, like, say, the Pentagon, or a stop sign, you could call it "polygonal."