Coordinates (mathematics)

Coordinates are numbers which describe the location of points in a plane or in space. For example, the height above sea level is a coordinate which is useful for describing points near the surface of the earth. A coordinate system, in a plane or in space, is a systematic method of assigning a pair or a triple of numbers to each point in the plane or in space (respectively) which describe its position uniquely. For example, the triple consisting of latitude, longitude and altitude (height above sea level) define a coordinate system near to the surface of the earth.

Coordinates may be defined in more general contexts. For example, if one is not interested in height, then latitude and longitude form a coordinate system on the surface of the earth, which is (approximately) a sphere. Coordinates such as these are also important in astronomy for describing the location of objects in the (night) sky: see Celestial coordinate systems for further examples. For simplicity, however, this article will restrict attention to coordinate systems in a plane and in space.