polar coordinate

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Either of two coordinates, the radius or the polar angle, that together specify the position of a point in a plane.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun either of two values that locate a point on a plane by its distance from a fixed pole and its angle from a fixed line passing through the pole