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parallax

[par-uh-laks]
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noun
  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?
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Origin of parallax

1585–95; < Greek parállaxis change, equivalent to parallak- (stem of parallássein to cause to alternate, equivalent to para- para-1 + allássein to vary, akin to állos other; see else, allo-) + -sis -sis
Related formspar·al·lac·tic [par-uh-lak-tik] /ˌpær əˈlæk tɪk/, adjectivepar·al·lac·ti·cal·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for parallax

Historical Examples

  • It is in like manner, however, that the parallax stars are selected.

    Lectures on Stellar Statistics

    Carl Vilhelm Ludvig Charlier

  • Parallax is greatest when the body is in the horizon, and disappears when it is at the zenith.

    Lectures in Navigation

    Ernest Gallaudet Draper

  • We have also ascertained that the annual parallax is about half a second.

    The Story of the Heavens

    Robert Stawell Ball

  • Of only about a hundred is the calculation of the parallax possible, so distant are they.

    The Other Side of Evolution

    Alexander Patterson

  • He concluded that the parallax of Alpha Lyr was about one-fourth of a second.


British Dictionary definitions for parallax

parallax

noun
  1. an apparent change in the position of an object resulting from a change in position of the observer
  2. astronomy the angle subtended at a celestial body, esp a star, by the radius of the earth's orbit. Annual or heliocentric parallax is the apparent displacement of a nearby star resulting from its observation from the earth. Diurnal or geocentric parallax results from the observation of a planet, the sun, or the moon from the surface of the earth
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Derived Formsparallactic (ˌpærəˈlæktɪk), adjectiveparallactically, adverb

Word Origin

C17: via French from New Latin parallaxis, from Greek: change, from parallassein to change, from para- 1 + allassein to alter
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for parallax

n.

1570s, from Middle French parallaxe (mid-16c.), from Greek parallaxis "change, alteration, inclination of two lines meeting at an angle," from parallassein "to alter, make things alternate," from para- (see para- (1)) + allassein "to change," from allos "other" (see alias). Related: Parallactic.

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Online Etymology Dictionary, © 2010 Douglas Harper

parallax in Medicine

parallax

(părə-lăks′)
n.
  1. The apparent displacement of an object caused by a change in the position from which it is viewed.
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Related formspar′al•lactic (-lăktĭk) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

parallax in Science

parallax

[părə-lăks′]
  1. A 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. The parallax of nearby stars caused by observing them from opposite points in Earth's orbit around the Sun is used in estimating the stars' distance from Earth through triangulation.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.