• synonyms


  1. a combining form meaning “self,” “same,” “spontaneous,” used in the formation of compound words: autograph, autodidact.
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Also especially before a vowel, aut-.

Origin of auto-1

< Greek, combining form of autós self


  1. a combining form representing automobile in compound words: autocade.
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Origin of auto-2

see origin at auto


  1. a combining form representing automatic in compound words: autoalarm; autofeed; autofocus. Sometimes also taken as an adjective: auto enlarger; auto stop control; auto dialer.
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Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for auto-


sometimes before a vowel aut-

combining form
  1. self; same; of or by the same oneautobiography
  2. acting from or occurring within; self-causedautohypnosis
  3. self-propelling; automaticautomobile
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Word Origin

from Greek autos self
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 auto-

word-forming element meaning "self, one's own, by oneself," from Greek auto- "self, one's own," combining form of autos "self, same," of unknown origin. Before a vowel, aut-; before an aspirate, auth-. In Greek also used as a prefix to proper names, e.g. automelinna "Melinna herself." The opposite prefix would be allo-.

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Online Etymology Dictionary, © 2010 Douglas Harper

auto- in Medicine


  1. Self; same:autogamy.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

auto- in Science


  1. A prefix meaning “oneself,” as in autoimmune, producing antibodies or immunity against oneself. It also means “by itself, automatic,” as in autonomic, governing by itself.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.