In Ordinate

In Ordinate the Cartesian system of co-ordinates, the distance of a point from the horizontal axis (axis of x) measured parallel to the axis of y. Thus PR is the ordinate of P. The word appears to have been first x used by Rene Descartes, and to be derived from lineae ordinatae, a term used by Roman surveyors for parallel lines. (See GEOMETRY: Ana- lytical.)