The coordinate Y is the ordinate – what do we call the coordinate X?
Cartesian coordinate system arbitrary. However, the orientation of the axes relative to each other should always comply with the right-hand rule, unless specifically stated otherwise. All laws of physics and math assume this right-handedness, which ensures consistency. For 3D diagrams, the names "abscissa" and "ordinate" are rarely used for "x" and "y", respectively. When they are, the "z"-coordinate is sometimes called the applicate. The words "abscissa", "ordinate" and "applicate" are sometimes used to refer to coordinate axes rather than the coordinate values. The axes of a two-dimensional Cartesian system divide the plane into four infinite regions, called quadrants, each bounded by two half-axes.
Cartesian coordinate system (However, in some computer graphics contexts, the ordinate axis may be oriented downwards.) The origin is often labeled "O", and the two coordinates are often denoted by the letters "X" and "Y", or "x" and "y". The axes may then be referred to as the "X"-axis and "Y"-axis. The choices of letters come from the original convention, which is to use the latter part of the alphabet to indicate unknown values. The first part of the alphabet was used to designate known values. A Euclidean plane with a chosen Cartesian coordinate system is called a "Cartesian plane". In a Cartesian