A plane is a flat two dimensional surface that extends indefinitely. A plane has zero thickness, infinite length and infinite width.

We often draw a shaded parallelogram to represent a plane with edges, but a plane has no edges.

Some real life examples of a plane are surfaces of a piece of paper, a wall, and a floor.

In this unit we learn about figures on a plane or plane figures. A plane figure is a geometric figure that has no thickness. A plane figure lies on only one plane. Plane figure can be made of lines, curves or both.

A plane figure can be closed or open.