Describe a figure of a closed curve that is not a polygon.
A circle is also a plane figure but it is not considered as a polygon, because it is a curved shape and does not have sides or angles. Therefore a circle is a closed curve that is not a polygon.
A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is constant.