A cube is not a polygon. To understand why, we need to look at the definitions of both terms.
A polygon is a two-dimensional geometric figure that consists of a finite number of line segments connected to form a closed shape. Common examples of polygons include triangles, rectangles, and pentagons. The key characteristics of polygons are that they exist in two dimensions (having length and width) and are flat.
On the other hand, a cube is a three-dimensional solid object. It has volume, depth, and is made up of six square faces. Each face of the cube is a polygon in itself, specifically a square, but when we talk about a cube as a whole, we refer to it as a polyhedron—not a polygon.
In summary, while a cube is composed of polygons (the square faces), it is not a polygon itself because it exists in three-dimensional space, unlike polygons, which are strictly two-dimensional forms.