Parallax
the difference of direction of a body as seen from two different points. It is generally applied to the direction of the heavenly bodies as seen from the earth's center and from some point of its surface. The parallax is greater the nearer the body and the greater the distance between the points in a direction at right angles to that of the body. The term is also applied to the difference in direction of a body seen from different points of the earth's orbit, the longest diameter of which is insufficient in case of some fixed stars.