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, n.
n. An ideal straight line joining the center of an
attracting body with that of a body describing an orbit around it, as a
line joining the sun and a planet or comet, or a planet and its
satellite.
