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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

Nuclear fusion is widely seen as a potential source of clean and sustainable energy.

From Science Daily • Jan. 4, 2026

Nuclear fusion occurs when two light atomic nuclei merge to form a single heavier one.

From The Wall Street Journal • Dec. 18, 2025

Nuclear fusion energy is generated when two nuclei are combined under intense heat and pressure, similar to how the sun works.

From Barron's • Dec. 18, 2025

Nuclear fusion is a slowly but very surely developing method of making clean energy.

From Los Angeles Times • Sep. 15, 2024

Nuclear fusion is the reaction that powers the sun.

From BBC • Oct. 12, 2023