—pl. radii vec•to•resPronunciation: (vek-tôr'ēz, -tōr'-), [key] radius vectors.
1. Math.the length of the line segment joining a fixed point or origin to a given point.
a. the straight line joining two bodies in relative orbital motion, as the line from the sun to a planet at any point in its orbit.
b. the distance between two such bodies at any point in the orbit.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.