A flat, closed figure is called a plane figure. A plane
figure can be made of straight lines, curved lines, or
both straight and curved lines.
Polygons are plane figures that are made of line segments. The
point where the sides meet is call the vertex
Example: All of these triangle are plane figures with 3 vertex and
3 sides. These triangles are polygons
A circle is a plane figure but not a polygon,because a circle
does not have any strait lines.