1. the apparent displacement of an observed object due to a change in the position of the observer.
2. Astronomy. the apparent angular displacement of a celestial body due to its being observed from the surface instead of from the center of the earth (diurnal parallax or geocentric parallax) or due to its being observed from the earth instead of from the sun (annual parallax or heliocentric parallax)
Compare parallactic ellipse.
3. the difference between the view of an object as seen through the picture-taking lens of a camera and the view as seen through a separate viewfinder.
4. an apparent change in the position of cross hairs as viewed through a telescope, when the focusing is imperfect.
5. Digital Technology. a 3D effect observed when images and other elements in the foreground of a screen move at a different rate than those in the background (often used attributively): parallax scrolling; Does this phone have parallax?
Origin: 1585-95; < Greek parállaxis change, equivalent to parallak- (stem of parallássein to cause to alternate, equivalent to para- para- + allássein to vary, akin to állos other; see else, allo-) + -sis -sis
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