A **plane** is a flat two-dimensional surface that extends infinitely into all directions. There are many different ways to represent a plane. In multivariable calculus, planes are usually represented in scalar form; that is,

or

In linear algebra, planes are usually represented in vector notation. This can be done in two ways. The first is to define a point on the plane and the vector normal to the plane; for example,

The scalar equation of this plane will be

A plane can also be defined by a point and two non-parallel vectors