fission

noun
fis·​sion | \ ˈfi-shᵊn How to pronounce fission (audio) , -zhᵊn\

Definition of fission

 (Entry 1 of 2)

1 : a splitting or breaking up into parts
2 : reproduction by spontaneous division of the body into two or more parts each of which grows into a complete organism
3 : the splitting of an atomic nucleus resulting in the release of large amounts of energy

fission

verb
fissioned; fissioning; fissions

Definition of fission (Entry 2 of 2)

intransitive verb

: to undergo fission

transitive verb

: to cause to undergo fission

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Other Words from fission

Noun

fissional \ ˈfi-​shə-​nəl How to pronounce fissional (audio) , -​zhə-​ \ adjective

Examples of fission in a Sentence

Recent Examples on the Web: Noun

One is fission reaction—the sort used in power stations. The Economist, "An accident in Russia points to the risks of atomic aviation," 15 Aug. 2019 But this work was only meant as a proof of concept of exciton fission in a solar cell. Daniel Oberhaus, WIRED, "New Designs Could Boost Solar Cells Beyond Their Limits," 11 July 2019 Fusion could deliver more energy more safely and with far less harmful radioactive waste than fission, but just a small number of people—including a 14-year-old from Arkansas—have managed to build working nuclear fusion reactors. National Geographic, "What is nuclear energy and is it a viable resource?," 26 Mar. 2019 The authors conclude that advanced fission designs have no hope at all of commercializing in the US by mid-century, which is when the US economy needs to be decarbonized. David Roberts, Vox, "The US is rapidly losing nuclear power. That’s profoundly concerning for climate change.," 11 July 2018 Forthwith, the issues multiply, as if by fission: What will people think? John Anderson, WSJ, "‘A Kid Like Jake’ Review: Cutthroat Kindergartens," 31 May 2018 David Poston, chief reactor designer at Los Alamos National Laboratory, said the Kilopower reactor is the first truly new fission reactor concept in the U.S. in more than 40 years. Grant Segall, cleveland.com, "NASA Glenn shares successful demonstration of nuclear power for space (photos)," 2 May 2018 Fusion, as the name suggests, is the exact opposite of fission. Michael Blaustein, Fox News, "Scientists say the dream of unlimited clean energy is about to come true," 12 Mar. 2018 Fusion reactors would be safer to operate and would generate much less radioactive waste than fission reactors. Hiawatha Bray, BostonGlobe.com, "MIT says nuclear fusion as a practical energy source is less than two decades away," 9 Mar. 2018

Recent Examples on the Web: Verb

The point is that by analyzing the array of radioactive fission products – those that can be captured and analyzed – nuclear forensic specialists can start to figure out if the atoms that fissioned were U-235, Pu-239, or (in some cases) U-238. Andrew Karam, Popular Mechanics, "Nuclear Forensics: How Scientists Can Tell Whether North Korea Is Lying About Its Bomb Test," 7 Jan. 2016 Anyone can see that fissioning uranium 235 or plutonium can be used to generate electricity. Scientific American, "Readers Respond to the January 2018 Issue," 1 Jan. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'fission.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of fission

Noun

circa 1617, in the meaning defined at sense 1

Verb

1929, in the meaning defined at intransitive sense

History and Etymology for fission

Noun

borrowed from Latin fissiōn-, fissiō, from fid-, variant stem of findere "to split, cleave" + -tiōn-, -tiō, suffix of verbal action — more at bite entry 1

Verb

derivative of fission entry 1

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More Definitions for fission

fission

noun

English Language Learners Definition of fission

physics : a process in which the nucleus of a heavy atom is split apart
biology : a kind of reproduction in which a cell or body divides into two or more parts and each part grows into a whole new individual

fission

noun
fis·​sion | \ ˈfi-shən How to pronounce fission (audio) \

Kids Definition of fission

1 : a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
2 : the process of splitting an atomic nucleus with the release of large amounts of energy

fission

noun
fis·​sion | \ ˈfish-ən also ˈfizh- How to pronounce fission (audio) \

Medical Definition of fission

1 : a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
b : the splitting of an atomic nucleus resulting in the release of large amounts of energy

called also nuclear fission

Other Words from fission

fission verb fissioned; fissioning\ ˈfish-​(ə-​)niŋ also ˈfizh-​ How to pronounce fissioning (audio) \
fissional \ ˈfish-​ən-​ᵊl also ˈfizh-​ How to pronounce fissional (audio) \ adjective

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