In a Cartesian coordinate system, the abscissa refers to the x-coordinate and the ordinate refers to the y-coordinate of a point. The abscissa is the horizontal distance of a point from the y-axis, scaled with the x-axis, while the ordinate is the vertical distance of a point from the x-axis, scaled with the y-axis. Together, the abscissa and ordinate are called coordinates. An ordered pair is used to denote a point in the Cartesian plane, with the abscissa as the first component and the ordinate as the second component.

For the z-axis in a three-dimensional Cartesian coordinate system, there is no widely accepted term like abscissa and ordinate. However, the term "applicate" has been used to refer to the z-coordinate in some sources.