Any numerically-defined position (either vertical or horizontal) relative to some point of origin. A graph—or other coordinate system—plots a point using a horizontal coordinate and a vertical coordinate defined with respect to an origin (0,0). Thus, a point having the coordinates (4,5) would be four units from the origin along the horizontal axis, and five units above the point of origin on the vertical; axis. Three-dimensional coordinate systems add a third coordinate representing depth.