What defines a polygon?

A polygon is defined as a two-dimensional (2D) closed shape that is formed by connecting a finite number of straight line segments end to end. Each line segment, known as a side, connects to another to create angles and vertices, resulting in a closed figure. This definition is critical in geometry, as it distinguishes polygons from other shapes by emphasizing the aspect of being both two-dimensional and closed.

In contrast, three-dimensional shapes made up of curves or open shapes consisting of straight lines do not meet the criteria for polygons. The distinction of having sides is fundamental to identifying polygons, while shapes that lack sides do not fall within this category. Understanding these characteristics is essential when classifying shapes in geometry.