PARALLAX

[par.al.lax] n [MF parallaxe, fr. Gk parallaxis, fr. parallassein to change, fr. para- + allassein to change, fr. allos other] (1580): the apparent displacement or the difference in apparent direction of an object as seen from two different points not on a straight line with the object; esp: the angular difference in direction of a celestial body as measured from two points on the earth's orbit