nucleus

noun
nu·​cle·​us | \ ˈnü-klē-əs How to pronounce nucleus (audio) , ˈnyü-\
plural nuclei\ ˈnü-​klē-​ˌī How to pronounce nuclei (audio) , 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

The appointment comes at a moment of turnover, if not turmoil, in the nucleus of those U.S. and Afghan officials who have been guiding the war effort. Craig Nelson, WSJ, "Mattis Makes Surprise Stop in Kabul for Talks With New U.S. Commander, Afghan Officials," 7 Sep. 2018 In comparing isotopes of an element like uranium, the atomic number stays the same, but the isotope number — the sum of the protons and neutrons in a nucleus — can differ. Umair Irfan, Vox, "Uranium enrichment will be a key point in talks with North Korea. Here’s what it is.," 11 June 2018 This is the first time scientists have sequenced full genomes of DNA from the cell’s nucleus. Kiona N. Smith, Ars Technica, "DNA may reconnect Aboriginal Australian remains with modern communities," 27 Dec. 2018 That massive cap spike in 2016 allowed the Warriors to sign Kevin Durant without sacrificing anyone from the nucleus that had won 73 games the year before. Andrew Sharp, SI.com, "The NBA is Broken, But Not Because of DeMarcus Cousins," 5 July 2018 The Oregon Ducks are poised to make a major splash on the recruiting trail this weekend, potentially adding to both this fall's roster and the 2019 future nucleus. Andrew Nemec, OregonLive.com, "John Miller, Junior Walling, 2020 Oregon HS LBs, discuss Oregon State Beavers, early recruiting process," 18 May 2018 Atomic nuclei clearly don’t readily convert into up-down quark matter either. Adrian Cho, Science | AAAS, "Weird new form of nuclear matter might lie just beyond experimenters' grasp," 15 May 2018 All-Metro seniors Matt Brandau (attackman), Michael Ubriaco (midfielder) and Chris Brandau (goalie) provide the nucleus for the Lakers with sophomore attackman Brendan Grimes a pure finisher. Glenn Graham, baltimoresun.com, "Breaking down the MIAA A Conference lacrosse playoffs," 10 May 2018 Amazon maintains its main nucleus of more than 40 buildings in Seattle but has somewhat gone back to its roots by expanding recently into Bellevue, albeit in shiny new office towers this time. Mike Rosenberg, The Seattle Times, "Bellevue house and garage where Jeff Bezos started Amazon up for sale," 11 Feb. 2019

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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Statistics for nucleus

Last Updated

15 Jun 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 How to pronounce nucleus (audio) , 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 How to pronounce nucleus (audio) \
plural nuclei\ -​klē-​ˌī How to pronounce nuclei (audio) \ 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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