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  1. the standard unit of electrical resistance in the International System of Units(SI), formally defined to be the electrical resistance between two points of a conductor when a constant potential difference applied between these points produces in this conductor a current of one ampere. The resistance in ohms is numerically equal to the magnitude of the potential difference. Symbol: Ω

Origin of ohm

First recorded in 1861; named after G. S. Ohm
Related formsohm·ic [oh-mik] /ˈoʊ mɪk/, adjective


  1. On His Majesty's Service; On Her Majesty's Service.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for ohms

Historical Examples

  • The resistance of the secondary wire should be from 100 to 150 ohms.

    Scientific American, Volume XLIII., No. 25, December 18, 1880


  • How far away is the break in the wire if the latter has a resistance of 80 ohms to the mile?


    Willis Eugene Tower

  • What current will flow in the circuit if the external resistance is 2.5 ohms?


    Willis Eugene Tower

  • The separate resistances of two incandescent lamps are 200 ohms and 70 ohms.


    Willis Eugene Tower

  • A pair of magnets of about 50 ohms are mounted on this support.

British Dictionary definitions for ohms


abbreviation for (in Britain and the dominions of the Commonwealth)
  1. On Her (or His) Majesty's Service


  1. the derived SI unit of electrical resistance; the resistance between two points on a conductor when a constant potential difference of 1 volt between them produces a current of 1 ampereSymbol: Ω

Word Origin

C19: named after Georg Simon Ohm


  1. Georg Simon (ˈɡeːɔrk ˈziːmɔn). 1787–1854, German physicist, who formulated the law named after him
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 ohms



unit of electrical resistance, 1867, in recognition of German physicist Georg S. Ohm (1789-1854), who determined the law of the flow of electricity. Originally proposed as ohma (1861) as a unit of voltage. Related: ohmage; ohmic; ohmeter.

Online Etymology Dictionary, © 2010 Douglas Harper

ohms in Medicine


n. Symbol Ω
  1. A unit of electrical resistance equal to that of a conductor in which a current of one ampere is produced by a potential of one volt across its terminals.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

ohms in Science


  1. The SI derived unit used to measure the electrical resistance of a material or an electrical device. One ohm is equal to the resistance of a conductor through which a current of one ampere flows when a potential difference of one volt is applied to it.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

ohms in Culture



The unit of electrical resistance, named after the nineteenth-century German physicist Georg Ohm.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.