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nuclear energy

American  
[noo-klee-er en-er-jee, nyoo-] / ˈnu kli ər ˈɛn ər dʒi, ˈnyu- /

noun

  1. energy released by reactions within atomic nuclei, as in nuclear fission or fusion.

nuclear energy British  

noun

  1. Also called: atomic energy.  energy released during a nuclear reaction as a result of fission or fusion

"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
nuclear energy Scientific  

  1. The energy released by the nucleus of an atom as the result of nuclear fission, nuclear fusion, or radioactive decay. The amount of energy released by the nuclear fission of a given mass of uranium is about 2,500,000 times greater than that released by the combustion of an equal mass of carbon. And the amount of energy released by the nuclear fusion of a given mass of deuterium is about 400 times greater that that released by the nuclear fission of an equal mass of uranium.

  2. Also called atomic energy

  3. Electricity generated by a nuclear reactor.

nuclear energy Cultural  

  1. Energy obtained from nuclear reactions.

Pronunciation

See nuclear ( def. ).

Etymology

Origin of nuclear energy

First recorded in 1925–30

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Against this backdrop, nuclear energy is re-emerging as a practical solution.

From The Wall Street Journal • Apr. 9, 2026

And nuclear energy seems to be back in fashion as part of a home-grown European energy mix - in the UK as well as the EU.

From BBC • Apr. 3, 2026

Morgan Stanley’s optimism is in line with the bullish, AI-driven, narrative around nuclear energy, which propelled Constellation Energy stock to gains of 58% in 2025 and 91% in 2024.

From Barron's • Mar. 25, 2026

Morgan Stanley’s optimism is in line with the bullish, AI-driven, narrative around nuclear energy, which propelled Constellation Energy stock to gains of 58% in 2025 and 91% in 2024.

From Barron's • Mar. 25, 2026

Still, the idea of attempting to release nuclear energy in the middle of a city of three million made Groves very nervous.

From "Bomb" by Steve Sheinkin

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.