nucleus

noun
nu·​cle·​us | \ ˈnü-klē-əs, ˈnyü-\
plural nuclei\ ˈnü-​klē-​ˌī , ˈnyü-​ \ also nucleuses

Definition of nucleus 

1a : the small bright body in the head of a comet
b : the small brighter and denser portion of a galaxy (see galaxy sense 1b)
2 : a central point, group, or mass about which gathering, concentration, or accretion takes place: such as
a : a cellular organelle of eukaryotes that is essential to cell functions (such as reproduction and protein synthesis), is composed of nucleoplasm and a nucleoprotein-rich network from which chromosomes and nucleoli arise, and is enclosed in a definite membrane — see cell illustration
b : a mass of gray matter or group of cell bodies of neurons in the central nervous system
c : a characteristic and stable complex of atoms or groups in a molecule (see molecule sense 1) especially : ring the naphthalene nucleus
d : the positively charged central portion of an atom that comprises nearly all of the atomic mass and that consists of protons and usually neutrons
3 : the peak of sonority in the utterance of a syllable
4 : a basic or essential part : core players who are the nucleus of the team

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Examples of nucleus in a Sentence

a college campus that was a nucleus of opposition to the war the nucleus of the movement's methodology has always been passive resistance

Recent Examples on the Web

Maria Goeppert-Mayer shared the 1962 prize with E. Paul Wigner and Hans Jensen for her work on the shell structure of atomic nuclei. Jennifer Ouellette, Ars Technica, "2018 physics Nobel Prize honors 3, including first woman in 55 years," 2 Oct. 2018 Future research can examine universes with different strengths of the strong nuclear force, the strongest known force between particles, which binds protons together in atomic nuclei, despite their mutual repulsion, Howe said. Charles Q. Choi, Space.com, "Why Alternate Universes Might Also Host Life Around their Stars," 26 Sep. 2018 The better the young nucleus looks, the better the odds of convincing an impact veteran of becoming a King. Jason Jones, sacbee, "Should Deandre Ayton and Luka Doncic be the Kings' only options at No. 2? | The Sacramento Bee," 18 May 2018 The spacecraft finally pierced the cometary veil of dust and shining glitter gas and produced the first image of the comet’s nucleus. Dennis Overbye, BostonGlobe.com, "Bradford Smith, 86, dies; showed postcards from outer space," 13 July 2018 The light arose from the collision between a remarkably energetic neutrino – a wraithlike subatomic particle moving close to the speed of light – and the nucleus of a hydrogen or oxygen atom deep within the ice. Eoin O'carroll, The Christian Science Monitor, "Neutrino demonstration heralds a new way of observing the cosmos," 12 July 2018 The spacecraft finally pierced the cometary veil of dust and shining glitter gas and produced the first image of the comet’s nucleus. Dennis Overbye, New York Times, "Bradford Smith, Who Showed Postcards From Outer Space, Dies at 86," 11 July 2018 That deft disappearing act forms the nucleus of Los Angeles artist Katherine Gray’s conceptual installations. R. Daniel Foster, latimes.com, "Vanishing act: Katherine Gray’s explorations in glass and light," 28 June 2018 Philadelphia, given the nucleus of young talent already in place, is thought to be a possibility. Ed Barkowitz, Philly.com, "Vegas covering itself in case LeBron James signs with the Sixers, gives Philly third-best odds at 2019 championship," 9 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'nucleus.' 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 nucleus

1668, in the meaning defined at sense 1a

History and Etymology for nucleus

New Latin, from Latin, kernel, from nuc-, nux nut — more at nut

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Last Updated

12 Jan 2019

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Time Traveler for nucleus

The first known use of nucleus was in 1668

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More Definitions for nucleus

nucleus

noun

English Language Learners Definition of nucleus

biology : the central part of most cells that contains genetic material and is enclosed in a membrane

physics : the central part of an atom that is made up of protons and neutrons

: a central or most important part of something

nucleus

noun
nu·​cle·​us | \ ˈnü-klē-əs, ˈnyü-\
plural nuclei\ -​klē-​ˌī \

Kids Definition of nucleus

1 : a usually round part of most cells that is enclosed in a double membrane, controls the activities of the cell, and contains the chromosomes
2 : the central part of an atom that comprises nearly all of the atomic mass and that consists of protons and neutrons
3 : a central point, group, or mass Those players are the nucleus of the team.

nucleus

noun
nu·​cle·​us | \ ˈn(y)ü-klē-əs \
plural nuclei\ -​klē-​ˌī \ also nucleuses

Medical Definition of nucleus 

1 : a cellular organelle of eukaryotes that is essential to cell functions (as reproduction and protein synthesis), is composed of nuclear sap and a nucleoprotein-rich network from which chromosomes and nucleoli arise, and is enclosed in a definite membrane
2 : a mass of gray matter or group of nerve cells in the central nervous system
3 : a characteristic and stable complex of atoms or groups in a molecule especially : ring sense 2 the naphthalene nucleus
4 : the positively charged central portion of an atom that comprises nearly all of the atomic mass and that consists of protons and neutrons except in hydrogen which consists of one proton only

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