# What Are Two Different Ways to Name a Plane?

A geometric plane can be named as a single letter, written in upper case and in cursive lettering, such as plane Q. A plane can also be named by identifying three separate points on the plane that do not form a straight line.

A plane in geometry is a flat surface extending infinitely in all directions, with zero thickness. These dimensions mean that it does not resemble any real surface or object. It is as if a piece of paper, whiteboard surface, or tabletop extended infinitely in all directions. While geometric planes do not have any real life applications, they are a useful geometric tool.

A geometric plane is the third step in a mathematical series that begins with a point and ends with a solid object. A point, which has zero dimensions, is located on a plane. Second in the series is a one dimensional line, which is defined by two separate points on a plane. A plane, third in the series and having two dimensions, can contain any number of points and lines. The last in the series is a solid, which exists in three dimensions.

Similar to how a line is defined by two separate points, a plane can be defined by any three points that do not exist on the same line. An example of this is plane ABC, given that points A, B and C are found on the plane and do not form one line.

Parallel planes are two planes that are the same distance apart at every point, extending infinitely. This means that they never intersect. Perpendicular planes are planes that each contain a line, where the two lines intersect and form a 90 degree angle. Two planes that are perpendicular to a third plane are either parallel to each other, or intersect at a point.

A coordinate plane is a plane that contains both an x-axis and a y-axis. These two axes are used to identify where points fall on the coordinate plane. Both the x and y-axes on a coordinate plane are numbered, with values on the x-axis moving in a positive direction from left to right, and values on the y-axis moving in a positive direction up from zero. The x-axis and y-axis on a coordinate plane are perpendicular, and the point at which they intersect at zero is called the origin.