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 Only uranium-235 can sustain the fission reaction that makes nuclear reactors tick, so turning the ore into usable fuel requires separating the uranium-238 out in a process called enrichment. Daniel Oberhaus, Wired, "Recycled Nuclear Waste Will Power a New Reactor," 27 Feb. 2020 It was allowed to keep 5,000 centrifuges to separate the uranium-235 isotope needed to induce a fission chain reaction. Jonathan Tirone | Bloomberg, Washington Post, "Iran’s Nuclear Program," 15 Nov. 2019 When the earthquake was detected, the active reactors automatically shut down their fission reactions. Courtney Linder, Popular Mechanics, "Russia is Sailing a 'Floating Chernobyl' Into the Arctic," 26 Aug. 2019 Excited by the theoretical frontiers opened by wartime research on nuclear fission, Dyson returned to Cambridge and concentrated on becoming a physicist. George Johnson, SFChronicle.com, "Freeman Dyson, physicist who wrestled with moral questions, dies," 29 Feb. 2020 In 1938, German chemists Otto Hahn and Fritz Strassmann discovered nuclear fission by splitting the nuclei of uranium into lighter elements. BostonGlobe.com, "In 1777, France recognized American independence.," 18 Dec. 2019 This, therefore, makes the fission theory extremely unlikely. Robert Forster, Washington Post, "Robin Brett, NASA scientist who studied ‘moon rocks,’ dies at 84," 24 Oct. 2019 Oklo’s Aurora advanced fission reactor would be able to produce 1.5 megawatts of power without needing to refuel, and also has the ability to turn nuclear waste into zero-carbon energy. Josh Siegel, Washington Examiner, "Daily on Energy: A coal-state Republican energy regulator tells the fossil fuel industry it will need to adapt," 18 Mar. 2020 Fusion reactions can’t snowball out of control if a reactor breaks, as existing fission nuclear reactors can; without the required heat and pressure to sustain it, fusion would just stop. Daniel Michaels, WSJ, "Fusion Startups Step In to Realize Decades-Old Clean Power Dream," 6 Feb. 2020 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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Time Traveler for fission

Time Traveler

The first known use of fission was circa 1617

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Statistics for fission

Last Updated

17 May 2020

Cite this Entry

“Fission.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fission. Accessed 29 May. 2020.

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More Definitions for fission

fission

noun
How to pronounce fission (audio)

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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More from Merriam-Webster on fission

Rhyming Dictionary: Words that rhyme with fission

Spanish Central: Translation of fission

Nglish: Translation of fission for Spanish Speakers

Britannica English: Translation of fission for Arabic Speakers

Britannica.com: Encyclopedia article about fission

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