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• nuclear fission
  nuclear fission

  noun

  fission.
• fission, nuclear
  fission, nuclear

  A nuclear reaction in which a single large nucleus splits into two or more smaller nuclei. In some cases, for example with uranium, energy is released in this process.

nuclear fission

American  

[noo-klee-er fish-uhn] / ˈnu kli ər ˈfɪʃ ən /

noun

1. fission.

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nuclear fission British  

noun

1. Sometimes shortened to: fission.  the splitting of an atomic nucleus into approximately equal parts, either spontaneously or as a result of the impact of a particle usually with an associated release of energy Compare nuclear fusion

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fission, nuclear Cultural  

1. A nuclear reaction in which a single large nucleus splits into two or more smaller nuclei. In some cases, for example with uranium, energy is released in this process.

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Pronunciation

See nuclear ( def. ).

Discover More

The fission of uranium 235, an isotope of uranium, supplies energy for nuclear reactors and atomic bombs (see also atomic bomb).

Etymology

Origin of nuclear fission

First recorded in 1885–90

Example Sentences

See Examples For:

nuclear fission fission, nuclear

As part of its energy surge, China has pushed rapid investment into the only technology that currently can decarbonize the planet at scale: nuclear fission and fusion.

From The Wall Street Journal ● Nov. 10, 2025

It is produced by nuclear fission for use in medical gauges and devices, but can also be a byproduct of nuclear reactors and weapons testing, the agency said.

From Los Angeles Times ● Aug. 19, 2025

Like all nuclear fission plants, they are controversial.

From BBC ● Feb. 26, 2025

Sam Altman, who also chairs Oklo, a nuclear fission microreactor start-up that’s set to go public this year, is backing the power source to satisfy the world’s growing energy needs, including from A.I.

From New York Times ● Mar. 21, 2024

As sources of electricity go, nuclear fission is incredibly efficient.

From "Meltdown" by Deirdre Langeland

Unlike fission, nuclear fusion generates “no long-lived radioactive waste,” Bechtel says, and unlike fossil fuels, it doesn’t involve burning finite resources and creating carbon emissions.

From The Wall Street Journal ● Apr. 6, 2026

Unlike fission, nuclear fusion does not release harmful radioactive byproducts that take thousands of years to decay.

From Los Angeles Times ● Dec. 13, 2022

Why is a conventional fission nuclear reactor not able to explode as a bomb?

From Textbooks ● Aug. 12, 2015

Arthur Godfrey has confessed to a growing interest in "atomic energy and fission, nuclear fission, and all those things."

From Time Magazine Archive