from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The capacity for work or vigorous activity: synonym: strength.
  • noun Exertion of vigor or power.
  • noun Vitality and intensity of expression.
  • noun Informal A nonphysical force or quality perceived as inhering in a particular place, person, or situation.
  • noun Usable heat or power.
  • noun A source of usable power, such as petroleum or coal.
  • noun The capacity of a physical system to do work.
  • noun A form, amount, or level of this capacity.

from The Century Dictionary.

  • noun The actual exertion of power; power exerted; strength in action; vigorous operation.
  • noun Activity considered as a characteristic; habitual putting forth of power or strength, physical or mental, or readiness to exert it.
  • noun The exertion of or capacity for a particular kind of force; action or the power of acting in any manner; special ability or agency: used of the active faculties or modes of action regarded severally, and often in the plural: as, creative energy; the energies of mind and body.
  • noun In the Aristotelian philos., actuality; realization; existence; the being no longer in germ or in posse, but in life or in esse: opposed to power, potency, or potentiality.
  • noun A fact of acting or actually being.
  • noun In rhetoric, the quality of awakening the imagination of the reader or hearer, and bringing the meaning of what is said home to him; liveliness.
  • noun In physics: Half the sum of the masses of the particles of a system each multiplied by the square of its velocity; half the vis viva. See vis viva.
  • noun Half the greatest value to which the sum of the masses of all the particles of a given system each multiplied by the square of its velocity, could attain except for friction, viscosity, and other forces dependent on the velocities of the particles; otherwise, the amount of work (see work) which a given system could perform were it not for resistance dependent on the velocities.
  • noun of water in motion, or in an elevated position;
  • noun of air in motion, as the wind;
  • noun the muscular energy of animals. To these might be added the energy of direct solar radiation, the energy of the tides, and some others of less importance. The source of all these forms of energy, except that of the tides, is to be found in the radiant energy of the sun.

from the GNU version of the Collaborative International Dictionary of English.

  • noun Internal or inherent power; capacity of acting, operating, or producing an effect, whether exerted or not.
  • noun Power efficiently and forcibly exerted; vigorous or effectual operation.
  • noun Strength of expression; force of utterance; power to impress the mind and arouse the feelings; life; spirit; -- said of speech, language, words, style.
  • noun (Physics) Capacity for performing work.
  • noun etc. (Physics) See under Accumulation, Conservation, Correlation, etc.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun The impetus behind all motion and all activity.
  • noun The capacity to do work.
  • noun physics A quantity that denotes the ability to do work and is measured in a unit dimensioned in mass × distance²/time² (ML²/T²) or the equivalent.
  • noun An intangible, modifiable force (often characterized as either 'positive' or 'negative') believed to emanate from a person, place or thing and which is (or can be) preserved and transferred in human interactions; shared mood or group habit; a vibe, a feeling, an impression.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a healthy capacity for vigorous activity
  • noun any source of usable power
  • noun enterprising or ambitious drive
  • noun the federal department responsible for maintaining a national energy policy of the United States; created in 1977
  • noun forceful exertion
  • noun (physics) a thermodynamic quantity equivalent to the capacity of a physical system to do work; the units of energy are joules or ergs
  • noun an imaginative lively style (especially style of writing)


from The American Heritage® Dictionary of the English Language, 4th Edition

[French énergie, from Late Latin energīa, from Greek energeia, from energos, active : en-, in, at; see en– + ergon, work; see werg- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Ancient Greek ἐνέργεια (energeia, "action, act, work"), from ἐνεργός (energos, "active"), from ἐν (en, "in") + ἔργον (ergon, "work").


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  • Dr. Karl offers compelling counter-arguments to some of the speculations of the BPP, although he points us toward the controversial energy source of * zero point energy* as the breakthrough discovery we can use to power our starships.

    Asimov's Science Fiction 2004

  • Rather, conventional energy strategies adopt the ‘energy trickle-down’ approach to social welfare and implicitly assume that if energy supplies are increased, these problems will take care of themselves.

    Chapter 8 2000

  • Take, for example, the two most important terms - the energy released by the fire and the energy recovered by the pot contents (“energy utilised” in the literature).

    4.1) Market research 1989

  • Since the energy possessed by coal only becomes available when the coal is made to undergo a chemical change, it is sometimes called _chemical energy_.

    An Elementary Study of Chemistry William McPherson

  • Now when this material is reduced by the process of digestion to simpler bodies with fewer molecules, such as carbon dioxid, urea, and water, the force stored up in the meat as potential energy becomes manifest and is used as active life-force known as _kinetic energy_.

    A Practical Physiology Albert F. Blaisdell

  • An important fact about energy is, that all energy _tends to take the form of heat energy_.

    The Outline of Science, Vol. 1 (of 4) A Plain Story Simply Told J. Arthur Thomson 1897

  • It must, one would think, have been the badness of the ` ` copy '' that induced the compositors to turn ` ` the nature and theory of the Greek verb '' into _the native theology of the Greek verb_; ` ` the conser < p 124 > vation of energy '' into the _conversation of energy_; and the ` ` Forest Conservancy

    Literary Blunders Henry Benjamin Wheatley 1877

  • DeSmog uncovered information that two of the three directors on the board of the Natural Resources Stewardship Project are registered energy industry lobbyists and senior executives of the High Park Advocacy Group, a Toronto-based lobby firm that specializes in �energy, environment and ethics. News of the Underwater World 2009

  • It is possible that the two states are similar to the difference between potential and kinetic energy; and we must remember that _energy is always noticed or experienced by us, as energy, in its expenditure, never in its accumulation_. [

    The Problems of Psychical Research Experiments and Theories in the Realm of the Supernormal Hereward Carrington 1919

  • In an ideal situation where you put food in, and all energy is spent cooling it and not random amounts of air, there wouldn't be a sizable difference in energy usage between a stocked and near empty freezer.

    Make Your Refrigerator Far More Efficient | Lifehacker Australia 2009

  • “We define [energy sovereignty] as you’re free to decide which type of fuel source you want to use,” says Luis Reyes, CEO of Kit Carson Electric Cooperative.

    How Indigenous Communities are Building Energy Sovereignty Natalie Peart 2021


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  • *bounces in his chair*

    September 12, 2008

  • "Hundreds of thousands, if not millions, of tenant farmers who had resided in rural hamlets, living off common land, suddenly found their ancient lifestyle upended by a long wave of privatization. Those newly free-floating laborers became another, equally essential, energy source for the Industrial Revolution, filling its cities and coketowns with a nearly inexhaustible supply of cheap labor. In a sense, the Industrial Revolution would never have happened if two distinct forms of energy had not been separated from the earth: coal and commoners."

    —Steven Johnson, The Ghost Map (New York: Penguin, 2006), 94

    October 1, 2008