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• nuclear fusion
  nuclear fusion

  noun

  fusion.
• fusion, nuclear
  fusion, nuclear

  The combining of two small atomic nuclei to form a larger nucleus, sometimes with the release of energy. (Compare nuclear fission.)

nuclear fusion

American  

[noo-klee-er fyoo-zhuhn, nyoo-] / ˈnu kli ər ˈfyu ʒən, ˈnyu- /

noun

1. fusion.

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nuclear fusion British  

noun

1. Sometimes shortened to: fusion.  a reaction in which two nuclei combine to form a nucleus with the release of energy Compare nuclear fission See also thermonuclear reaction

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fusion, nuclear Cultural  

1. The combining of two small atomic nuclei to form a larger nucleus, sometimes with the release of energy. (Compare nuclear fission.)

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Pronunciation

See nuclear ( def. ).

Discover More

The use of fusion as a controllable energy source on Earth is still in its experimental stages.

The fusion of hydrogen into helium releases huge amounts of energy and is the main energy source of stars, including the sun.

Hydrogen bombs use the energy of fusion.

Etymology

Origin of nuclear fusion

First recorded in 1895–1900

Example Sentences

Being accused of attempting the impossible is not unusual for the scientists and engineers working on nuclear fusion projects around the world.

From BBC • Apr. 20, 2026

In 25 years, Mike Bechtel thinks we will have a new source of clean, abundant energy: nuclear fusion.

From The Wall Street Journal • Apr. 6, 2026

The instrument is TAE Technologies, a Foothill Ranch-based company working to develop the technology of nuclear fusion as a clean energy source.

From Los Angeles Times • Mar. 3, 2026

DJT’s recent moves include the launch of five ETFs focused on defense and energy sectors, and a merger agreement with nuclear fusion company TAE Technologies.

From Barron's • Feb. 18, 2026

Luckily for us, stars don’t collapse because there is another force at work: nuclear fusion.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife