Eccentric-anomaly Definition

(astronomy, celestial mechanics) The angle PCR formed by P = the periapsis of a celestial body's elliptical orbit, C = the center of that elliptical orbit, and R = the corresponding point to that celestial body (the projection of the celestial body along a direction parallel to the minor axis of its orbit onto the auxiliary circle (a circle which shares a diameter with the major axis of the celestial body's orbit)).