See more synonyms for energy on
noun, plural en·er·gies.
  1. the capacity for vigorous activity; available power: I eat chocolate to get quick energy.
  2. an adequate or abundant amount of such power: I seem to have no energy these days.
  3. Often energies. a feeling of tension caused or seeming to be caused by an excess of such power: to work off one's energies at tennis.
  4. an exertion of such power: She plays tennis with great energy.
  5. the habit of vigorous activity; vigor as a characteristic: Foreigners both admire and laugh at American energy.
  6. the ability to act, lead others, effect, etc., forcefully.
  7. forcefulness of expression: a writing style abounding with energy.
  8. Physics. the capacity to do work; the property of a system that diminishes when the system does work on any other system, by an amount equal to the work so done; potential energy. Symbol: E
  9. any source of usable power, as fossil fuel, electricity, or solar radiation.

Origin of energy

1575–85; < Late Latin energīa < Greek enérgeia activity, equivalent to energe- (stem of energeîn to be active; see en-2, work) + -ia -y3
Related formshy·per·en·er·gy, nounself-en·er·gy, noun

Synonyms for energy

See more synonyms for on Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for energy

Contemporary Examples of energy

Historical Examples of energy

  • He had sat in the background, but he had found both money and energy.

  • He rose with the blow; all his energy, from wrist to instep, was in that lifting drive.

  • Then abruptly, the young man spoke with the energy of perfect faith in the woman.

    Within the Law

    Marvin Dana

  • You have health and energy, and you have youth, which I haven't.


    Mary Roberts Rinehart

  • The Satanic energy of this outburst proclaims its author, Marlowe.

British Dictionary definitions for energy


noun plural -gies
  1. intensity or vitality of action or expression; forcefulness
  2. capacity or tendency for intense activity; vigour
  3. vigorous or intense action; exertion
  4. physics
    1. the capacity of a body or system to do work
    2. a measure of this capacity, expressed as the work that it does in changing to some specified reference state. It is measured in joules (SI units)Symbol: E
  5. a source of powerSee also kinetic energy, potential energy

Word Origin for energy

C16: from Late Latin energīa, from Greek energeia activity, from energos effective, from en- ² + ergon work
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 energy

1590s, "force of expression," from Middle French énergie (16c.), from Late Latin energia, from Greek energeia "activity, operation," from energos "active, working," from en "at" (see en- (2)) + ergon "work, that which is wrought; business; action" (see urge (v.)).

Used by Aristotle with a sense of "force of expression;" broader meaning of "power" is first recorded in English 1660s. Scientific use is from 1807. Energy crisis first attested 1970.

Online Etymology Dictionary, © 2010 Douglas Harper

energy in Medicine


  1. The capacity for work or vigorous activity; vigor; power.
  2. The capacity of a physical system to do work.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

energy in Science


  1. The capacity or power to do work, such as the capacity to move an object (of a given mass) by the application of force. Energy can exist in a variety of forms, such as electrical, mechanical, chemical, thermal, or nuclear, and can be transformed from one form to another. It is measured by the amount of work done, usually in joules or watts. See also conservation of energy kinetic energy potential energy. Compare power work.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

energy in Culture


In physics, the ability to do work. Objects can have energy by virtue of their motion (kinetic energy), by virtue of their position (potential energy), or by virtue of their mass (see E = mc2).


The most important property of energy is that it is conserved — that is, the total energy of an isolated system does not change with time. This is known as the law of conservation of energy. Energy can, however, change form; for example, it can be turned into mass and back again into energy.
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.