[dee-vee-ey-shuh n]
See more synonyms for deviation on
  1. the act of deviating.
  2. departure from a standard or norm.
  3. Statistics. the difference between one of a set of values and some fixed value, usually the mean of the set.
  4. Navigation. the error of a magnetic compass, as that of a ship, on a given heading as a result of local magnetism.Compare variation(def 8).
  5. Optics.
    1. Also called deflection.the bending of rays of light away from a straight line.
    2. angle of deviation.
  6. departure or divergence from an established dogma or ideology, especially a Communist one.

Origin of deviation

1375–1425; late Middle English (< Middle French) < Medieval Latin dēviātiōn- (stem of dēviātiō), equivalent to Late Latin dēviāt(us) (see deviate) + -iōn- -ion
Related formsde·vi·a·to·ry [dee-vee-uh-tawr-ee, -tohr-ee] /ˈdi vi əˌtɔr i, -ˌtoʊr i/, de·vi·a·tive, adjectivenon·de·vi·a·tion, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for deviation


  1. an act or result of deviating
  2. statistics the difference between an observed value in a series of such values and their arithmetic mean
  3. the error of a compass due to local magnetic disturbances
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 deviation

1640s, noun of action from deviate (v.). Statistical sense is from 1858. Related: Deviational.

Online Etymology Dictionary, © 2010 Douglas Harper

deviation in Medicine


  1. A turning away or aside from a normal course.
  2. An abnormality.
  3. Deviant behavior or attitudes.
  4. The difference, especially the absolute difference, between one number in a set and the mean of the set.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

deviation in Science


  1. The difference between one number in a set and the mean of the set.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.