Our online medical glossary of medical terms and definitions includes definitions for terms related to treatment, and general medicine
RADIUS VECTOR
1. A straight line (or the length of such line) connecting any point, as of a curve, with a fixed point, or pole, round which the straight line turns, and to which it serves to refer the successive points of a curve, in a system of polar coordinates. See Coordinate.
2. An ideal straight line joining the center of an attracting body with that of a body describing an orbitnear it, as a line joining the sun and a planet or comet, or a planet and its satellite.
Source: Websters Vocabulary