Coordinates

A coordinate system is a system assigning a number (or tuple of numbers) to every point on an entity. The number (or tuple of numbers) assigned to a point is called the coordinate (or coordinates) of the point.

Examples

Longitude and latitude are a coordinate system for the surface of the earth.

If one picks two lines on a plane which meet at right angles, then one has implicitly chosen a Cartesian coordinate system for the plane.