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energy Line breaks: en¦ergy
Pronunciation: /ˈɛnədʒi/

Definition of energy in English:

noun (plural energies)

[mass noun]
1The strength and vitality required for sustained physical or mental activity: changes in the levels of vitamins can affect energy and well-being
More example sentences
  • The mental activity consumes energy and can, in the event of excess, lead to overstrain.
  • The main modifiable factors affecting energy balance are dietary energy intake and energy expended through physical activity.
  • When people are under stress, they don't have as much energy for physical or mental activity.
vitality, vigour, life, liveliness, animation, vivacity, spirit, spiritedness, fire, passion, ardour, zeal, verve, enthusiasm, zest, vibrancy, spark, sparkle, effervescence, exuberance, buoyancy, perkiness, sprightliness;
strength, stamina, forcefulness, power, might, potency, dynamism, drive, push
informal zip, zing, pep, pizzazz, punch, bounce, fizz, oomph, go, get-up-and-go, vim and vigour
North American informal feistiness
1.1 (energies) A person’s physical and mental powers: an alternative is to devote your energies to voluntary work
More example sentences
  • There is a need to focus mental energies and prepare yourself to face competition.
  • You are a physical person, but you know how to control and use of your physical energies.
  • I was amazed at the creative energies expended in getting people to give and increase their pledges.
2Power derived from the utilization of physical or chemical resources, especially to provide light and heat or to work machines: nuclear energy
More example sentences
  • These include global warming, energy efficiency and renewable energy resources.
  • It will also provide virtually unlimited energy and material resources for humankind.
  • That efficiency will include solar power, recyclable energy and heat retention.
3 Physics The property of matter and radiation which is manifest as a capacity to perform work (such as causing motion or the interaction of molecules): a collision in which no energy is transferred
More example sentences
  • Why is that electrons radiate electromagnetic energy when they are accelerated?
  • If a particle moves faster than the speed of light, it must create a shockwave, and radiate energy.
  • The protons are set in motion and, being charged, they again deposit energy through electrical interactions.


Mid 16th century (denoting force or vigour of expression): from French énergie, or via late Latin from Greek energeia, from en- 'in, within' + ergon 'work'.

  • work from Old English:

    Work is connected with the Greek word ergon, which is the source of energy (late 16th century), ergonomic [1950s], and surgeon. Wrought, meaning ‘made in a particular way’ and found in wrought iron (early 18th century), is the old past form of work, which people used where we now use worked. Wright, a common surname that means ‘maker’ and is found in words such as shipwright (Old English) and wheelwright (Middle English), is also closely related to work. The first workaholic was mentioned in 1968. Since then we have had chocaholics and shopaholics, but the first word to be formed in this way from alcoholic was foodaholic, in 1965. The dictum ‘Work expands so as to fill the time available’ is known as Parkinson's law. It was first expressed by Professor C. Northcote Parkinson in 1955. Much older is the proverb All work and no play makes Jack a dull boy, which is first found in 1659. See also devil

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