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[jool, joul]
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noun Physics.
  1. the standard unit of work or energy in the International System of Units(SI), equal to the work done by a force of one newton when its point of application moves through a distance of one meter in the direction of the force: equivalent to 107 ergs and one watt-second. Abbreviation: J, j

Origin of joule

First recorded in 1885–90; named after J. P. Joule
Also called newton-meter.


[jool, joul]
  1. James Prescott,1818–89, English physicist.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for joule

Historical Examples

  • We know this from Playfair, who mentioned it at Joule's death.

    The Conquest of Bread

    Peter Kropotkin

  • Joule of Manchester was the first to verify Mayer's law quantitatively.

  • This is known as the mechanical equivalent of heat, or Joule's equivalent.

  • Mr. Joule's first investigations were in the field of magnetism.

  • This is the law known as the conservation of energy which has been built up by Helmholtz, Thomson, Joule and others.

British Dictionary definitions for joule


  1. the derived SI unit of work or energy; the work done when the point of application of a force of 1 newton is displaced through a distance of 1 metre in the direction of the force. 1 joule is equivalent to 1 watt-second, 10 7 ergs, 0.2390 calories, or 0.738 foot-poundSymbol: J

Word Origin

C19: named after James Prescott Joule


  1. James Prescott. 1818–89, English physicist, who evaluated the mechanical equivalent of heat and contributed to the study of heat and electricity
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 joule


unit of electrical energy, 1882, coined in recognition of British physicist James P. Joule (1818-1889).

Online Etymology Dictionary, © 2010 Douglas Harper

joule in Medicine


  1. The International System unit of electrical, mechanical, and thermal energy.
  2. A unit of electrical energy equal to the work done when a current of 1 ampere is passed through a resistance of 1 ohm for 1 second.
  3. A unit of energy equal to the work done when a force of 1 newton acts through a distance of 1 meter.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

joule in Science


[jōōl, joul]
  1. The SI derived unit used to measure energy or work. One joule is equal to the energy used to accelerate a body with a mass of one kilogram using one newton of force over a distance of one meter. One joule is also equivalent to one watt-second.


  1. British physicist who demonstrated that heat is a form of energy. His work established the law of conservation of energy, stating that energy is never destroyed but may be converted from one form into another. The joule unit of energy is named for him.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.