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Word of the Day
Tuesday, June 27, 2017

Definitions for parallax

  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.

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Citations for parallax
It is hard for a man walking rapidly along like Arthur not to mistake the parallax of objects in the different planes for the motion of a person in the shadows ... Paul Goodman, The Empire City: A Novel of New York City, 1959
Voices ... come from everywhere and nowhere, sometimes catching up with lips, sometimes floating in the general parallax that sitting near the sides of the Penthouse Theater (where the movie opened yesterday) brings on. Renata Adler, "Petula Clark and Fred Asaire Head Cast: 2 Other Movies Begin Local Engagements," New York Times, October 10, 1968
Origin of parallax
Parallax drifts into Mr. Leopold Bloom’s head about 1:00 in the afternoon as he is walking to Davy Byrne’s pub for lunch (Episode 8, “Lestrygonians,” of Ulysses), and he attempts a partial etymology: “ParallaxPar it’s Greek: parallel, parallax.” Parallel and parallax both come from the same Greek elements: the preposition and combining form pará- “beside, from beside” and the adjective állos “other.” Parállēlos “beside one another, side by side” comes from pará- and the reciprocal pronoun allḗlōn “each other,” a derivative of állos. The second element of parállaxis is from another derivative of állos, the verb allássein (one of whose inflectional stems is allag-) “to make other, change.” Both parállēlos and parállaxis are most common in Hellenistic Greek technical and scientific works, e.g., in medicine, geometry, cartography, and astronomy. Parallax entered English in the 16th century.