In mathematics, a *plane* is a [[Euclidean Geometry|Euclidean]], two-dimensional surface that extends indefinitely. A plane is the two-dimensional analogue of a [[point]] (zero dimensions), a [[Line, Line-Segment, Ray|line]] (one dimension) and three-dimensional space. Planes can arise as subspaces of some higher-dimensional space, as with one of a room's walls, infinitely extended, or they may enjoy an independent existence in their own right, as in the setting of two-dimensional Euclidean geometry. Sometimes the word plane is used more generally to describe a two-dimensional surface including [[Non-Euclidean Geometry]] When working exclusively in two-dimensional Euclidean space, the definite article is used, so the plane refers to the whole space. Many fundamental tasks in mathematics, geometry, trigonometry, graph theory, and graphing are performed in a two-dimensional space, often in the plane. ![[def-pnt-ln-pln.svg|-dmo-noinv]]