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[en-er-jee] /ˈɛn ər dʒi/
noun, plural energies.
the capacity for vigorous activity; available power:
I eat chocolate to get quick energy.
an adequate or abundant amount of such power:
I seem to have no energy these days.
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.
an exertion of such power:
She plays tennis with great energy.
the habit of vigorous activity; vigor as a characteristic:
Foreigners both admire and laugh at American energy.
the ability to act, lead others, effect, etc., forcefully.
forcefulness of expression:
a writing style abounding with energy.
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.
any source of usable power, as fossil fuel, electricity, or solar radiation.
1575-85; < Late Latin energīa < Greek enérgeia activity, equivalent to energe- (stem of energeîn to be active; see en-2, work) + -ia -y3
Related forms
hyperenergy, noun
self-energy, noun
1. vigor, force, potency. 5. zeal, push. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for energy
  • Also essential were the thrust of power, the lift of influence, the energy of competing egos.
  • Scientists have invented a plastic solar cell that can turn the sun's power into electrical energy, even on a cloudy day.
  • But what was in their own power they tried to handle divinely, with real energy.
  • More nonsense gets spewed about nuclear power than any other form of energy.
  • energy regulators removed reports on power plants, transmission lines, and the transportation of radioactive materials.
  • Self-contained power plants could supply growing energy demand in poor countries.
  • Here, the exterior will sport photovoltaic cells to collect solar power and make the building energy self-sufficient.
  • Offshore energy has been in the news of late.
  • Go green with these energy-saving lightbulbs.
  • You don't have to shiver in the dark to reduce your home energy costs.
British Dictionary definitions for energy


noun (pl) -gies
intensity or vitality of action or expression; forcefulness
capacity or tendency for intense activity; vigour
vigorous or intense action; exertion
  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) E
a source of power See also kinetic energy, potential energy
Word Origin
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
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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
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energy in Medicine

energy en·er·gy (ěn'ər-jē)

  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.
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energy in Science
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 © 2002. Published by Houghton Mifflin. All rights reserved.
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energy in Culture

energy definition

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).

Note: 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 American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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