Definition of energy in US English:



  • 1The strength and vitality required for sustained physical or mental activity.

    ‘changes in the levels of vitamins can affect energy and well-being’
    • ‘A man may want to do much, but he has only so much time, only so much mental and physical energy.’
    • ‘And few here have either the energy or strength to walk that far in a scorching African sun.’
    • ‘Commentators explained that this gave them instant and sustained energy.’
    • ‘Combining this dish with oatcakes or wholegrain bread makes a perfect protein meal, which will sustain energy longer.’
    • ‘What I was about to do would require a lot of energy, stamina, and vocal power.’
    • ‘If you think there is no way of having the energy and strength you desire, think again.’
    • ‘No job was ever too big for her to tackle, and at the end of a long day she still had energy for the social activities she so greatly enjoyed.’
    • ‘I'm really looking forward to working in London - so much energy and activity on the doorstep.’
    • ‘From this position very little strength or energy is required for him to complete the throw.’
    • ‘The mental activity consumes energy and can, in the event of excess, lead to overstrain.’
    • ‘Communities and voluntary organisations often contain the necessary energy and enthusiasm required to make a difference.’
    • ‘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.’
    • ‘After six hours of work at school, students have little mental and physical energy to do more work at home.’
    • ‘It allows him to drain his opponents of any form of energy that they possess.’
    • ‘He possessed formidable physical and mental energy, tremendous discipline.’
    • ‘She felt weak, as if she had just spent every bit of energy she had ever possessed.’
    • ‘Diane would have made me go anyway, and I didn't posses enough mental or physical energy to put up a fight.’
    • ‘A way of limiting the amount of time and energy spent on the activity.’
    • ‘We want to encourage people to donate their time and energy to voluntary activities and we want to see voluntary organisations free to do the work they are set up to do.’
    vitality, vigour, life, liveliness, animation, vivacity, spirit, spiritedness, fire, passion, ardour, zeal, verve, enthusiasm, zest, vibrancy, spark, sparkle, effervescence, exuberance, buoyancy, perkiness, sprightliness
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    1. 1.1energies A person's physical and mental powers, typically as applied to a particular task or activity.
      • ‘He returned to the unquestioning dream world of his childhood and put his energies, at last, into this book.’
      • ‘The competition for children's minds and energies is so different to my early years.’
      • ‘When he was able finally to go home, the reunion with his father absorbed his energies.’
      • ‘There is a need to focus mental energies and prepare yourself to face competition.’
      • ‘Feeling unable to change the situation in my life, I started to channel all my energies into controlling my weight.’
      • ‘I was amazed at the creative energies expended in getting people to give and increase their pledges.’
      • ‘She rolls her eyes and buries her energies in consuming her noodles.’
      • ‘You are a physical person, but you know how to control and use of your physical energies.’
      • ‘You combine different aspects and integrate energies to bring success after a period of struggle.’
  • 2Power derived from the utilization of physical or chemical resources, especially to provide light and heat or to work machines.

    • ‘Fuel cells directly produce power by converting chemical energy into electrical energy.’
    • ‘We should be finding cleaner energy resources, but in a responsible manner.’
    • ‘A rational and practical management of energy resources is imperative.’
    • ‘The waste recycling plant, it is claimed, would provide enough energy to run the new factory and power the whole village.’
    • ‘At the same time, there is a increase in the efficiency with which energy is converted to heat.’
    • ‘I'm delighted that our local communities and voluntary groups are taking the lead on renewable energy for lighting and heating.’
    • ‘So I began to worry about where all the energy for lighting, powering the machines and everything came from.’
    • ‘It will also provide virtually unlimited energy and material resources for humankind.’
    • ‘Why not have a look at the real solutions such as renewable power sources and better energy efficiency?’
    • ‘These recharge 40 lithium batteries that provide the energy to power its two propellers.’
    • ‘At first, the program focused mainly on the use of nuclear energy for power generation.’
    • ‘That efficiency will include solar power, recyclable energy and heat retention.’
    • ‘The first is that, like oil, nuclear energy is a finite resource.’
    • ‘These include global warming, energy efficiency and renewable energy resources.’
    • ‘It would provide enough energy to power about 29,000 homes.’
    • ‘Their strategy was for the first round to rely heavily on nuclear electricity and energy efficiency.’
    • ‘They has previously used nuclear energy to power spacecraft but never in a propulsion system.’
    • ‘This system provides higher reliability and improved energy efficiency.’
    • ‘Wood provided needed energy for heat, fuel, and cooking as well as for construction of houses, tools, furniture, and ships.’
    • ‘However, some are still not efficient enough to turn chemical energy into mechanical power.’
  • 3Physics
    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’
    • ‘These convert infrared, ultraviolet and visible light into energy at a higher efficiency.’
    • ‘The protons are set in motion and, being charged, they again deposit energy through electrical interactions.’
    • ‘If a particle moves faster than the speed of light, it must create a shockwave, and radiate energy.’
    • ‘Why is that electrons radiate electromagnetic energy when they are accelerated?’
    • ‘That means that regardless of how much energy the electron has, it could never hope to be able to exit the box.’
    1. 3.1 A degree or level of energy possessed by something or required by a process.
      ‘gamma rays at different energies’
      • ‘These particles should appear in profusion only at the very high energies at which the unification takes place.’
      • ‘The enormous energies required to do this are needed to reveal the quantum nature of gravity.’
      • ‘These beams have different energies and properties which determine the depth that the beam penetrates into the body.’
      • ‘We have seen that in an atom, possible electron energies come in a discrete series of distinct levels.’
      • ‘Each different group of minerals acts in different ways to energies around them.’


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