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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

Actual power from nuclear fusion “has seemingly always been 10 to 20 years away,” Levin said.

From MarketWatch • May 18, 2026

Musk’s complaint also alleges that Altman engaged in self-dealing by directing OpenAI to pursue deals with companies in which he also held a personal stake, including nuclear fusion power company Helion.

From Los Angeles Times • May 12, 2026

Zilis recounted an OpenAI board meeting during which the AI lab was considering striking a deal with nuclear fusion startup Helion.

From The Wall Street Journal • May 6, 2026

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

Like nuclear fusion, it’s not easy to explain but it had an enormous effect.

From "The Story of Music" by Howard Goodall