A polygon is a closed shape with straight sides. Rectangles, triangles, hexagons, and octagons are all examples of a polygon.
The word polygon comes from the Greeks, like most terms in geometry, which they invented. It simply means many (poly) angles (gon). A polygon can’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."
