parallax
nounA change in the apparent position of an object relative to more distant objects, caused by a change in the observer’s line of sight towards the object.
nounAn apparent displacement of an object observed, due to real displacement of the observer, so that the direction of the former with reference to the latter is changed.
nounIn optics, an apparent shifting of the spider-lines in a telescope-reticle as the eye is moved before the eyepiece: it is due to the non-coincidence of the threads with the focal plane of the object-glass.
nounThe apparent displacement, or difference of position, of an object, as seen from two different stations, or points of view.
nounThe apparent difference in position of a body (as the sun, or a star) as seen from some point on the earth’s surface, and as seen from some other conventional point, as the earth’s center or the sun.
nounThe annual parallax. See annual parallax, below.
nounthe greatest value of the heliocentric parallax, or the greatest annual apparent change of place of a body as seen from the earth and sun; it is equivalent to the parallax of an astronomical object which would be observed by taking observations of the object at two different points one astronomical unit (the distance of the Earth from the sun) apart, if the line joining the two observing points is perpendicular to the direction to the observed object. The distance of an astronomical object from the Earth is inversely proportional to the
the apparent difference in position of an object as seen separately by one eye, and then by the other, the head remaining unmoved.
nounthe parallax of a body with reference to the earth’s center. This is the kind of parallax that is generally understood when the term is used without qualification.
