fission

1 of 2

noun

fis·​sion ˈfi-shᵊn How to pronounce fission (audio)
-zhᵊn
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
fissional adjective

fission

2 of 2

verb

fissioned; fissioning; fissions

intransitive verb

: to undergo fission

transitive verb

: to cause to undergo fission

Examples of fission in a Sentence

Recent Examples on the Web
Noun
Most of the three-hour movie, about the creation of the atomic bomb, is guys in suits, talking about fission and geopolitics and other brainy matters over a pulsating score by Ludwig Goransson. Alissa Wilkinson, New York Times, 3 Mar. 2024 How long can these Oppy-free lineups withstand the fission blast of the awards to come for Christopher Nolan’s movie? Joe Reid, Vulture, 16 Jan. 2024 Today, every American nuclear plant uses light water reactors, in which water is pumped into a reactor core and heated by atomic fission, producing steam to create electricity. Brad Plumer, New York Times, 12 Nov. 2023 To meet the goal of 1,110 GW in 2050, the world must break that trend and add new fission reactors at an unprecedented rate. IEEE Spectrum, 23 Jan. 2024 In modern weapons, plutonium fission ignites a second, more powerful stage in which hydrogen atoms undergo nuclear fusion, releasing even more energy. Sarah Scoles, Scientific American, 14 Nov. 2023 Increases in weapons’ explosive power required the creation of new metrics: from kilotons (equivalent to the energy released by 1,000 tons of TNT) for the original fission weapons to megatons (equivalent to that released by one million tons) for hydrogen fusion bombs. Henry A. Kissinger, Foreign Affairs, 13 Oct. 2023 After all these tests, nuclear scientists have a good idea of the radioactive fission products created in each explosion and the size of the particulates. Philippe and co-fed this data into a computer model that simulates the way particles disperse in the atmosphere. Discover Magazine, 26 July 2023 By using fusion to power a thermonuclear reaction, H-bomb explosions can be massively more powerful than fission reactions, like that in Gadget. Kelsey Atherton, Vulture, 26 July 2023
Verb
Most atoms do not fission, but the isotopes of certain elements, such as uranium-235, are fissile. Washington Post, 28 Apr. 2022 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, 7 Jan. 2016 Anyone can see that fissioning uranium 235 or plutonium can be used to generate electricity. Scientific American, 1 Jan. 2018

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'fission.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

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

First Known Use

Noun

circa 1617, in the meaning defined at sense 1

Verb

1929, in the meaning defined at intransitive sense

Time Traveler
The first known use of fission was circa 1617

Dictionary Entries Near fission

Cite this Entry

“Fission.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fission. Accessed 19 Mar. 2024.

Kids Definition

fission

1 of 2 noun
fis·​sion ˈfish-ən How to pronounce fission (audio)
 also  ˈfizh-
1
: a splitting or breaking up into parts
2
: 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
3
: the splitting of an atomic nucleus resulting in the release of large amounts of energy

fission

2 of 2 verb
fissioned; fissioning
ˈfish-(ə-)niŋ,
ˈfizh-
: to go through or cause to go through fission

Medical Definition

fission

noun
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
b
: the splitting of an atomic nucleus resulting in the release of large amounts of energy

called also nuclear fission

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

More from Merriam-Webster on fission

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