The right line drawn through the two points of contact of
   the two tangents drawn from a given point to a given conic section. The
   given point is called the pole of the line. If the given point lies
   within the curve so that the two tangents become imaginary, there is
   still a real polar line which does not meet the curve, but which
   possesses other properties of the polar. Thus the focus and directrix
   are pole and polar. There are also poles and polar curves to curves of
   higher degree than the second, and poles and polar planes to surfaces
   of the second degree.