Plane

Plane, in mathematics, surface having only length and breadth, any 2 points of which can be joined by a straight line composed entirely of points also in the plane. A plane may be determined by 2 intersecting or parallel lines, by a line and a point that does not lie on the line, or by 3 points that do not lie in a straight line. The intersection of 2 planes is a straight line; the intersection of a plane and a line in a different plane is a point. An infinite number of planes may pass through a single point or line. A plane is parallel to another plane if all perpendiculars drawn between them are of equal length.