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

While New York fans are still reeling from the organization missing out on big free agents Kevin Durant and Kyrie Irving, their future nucleus will be on display in Vegas, starting with Barrett. Scott Gleeson, USA TODAY, "Zion Williamson headlines another fascinating year at NBA summer league in Las Vegas," 5 July 2019 Each element of the periodic table is a particular kind of atom, ordered by the number of protons in its nucleus. Andrew Crumey, WSJ, "‘Mendeleyev’s Dream’ and ‘Elemental’ Review: Cracking the Chemical Code," 21 June 2019 Because Trae Young’s rookie season was a smashing success and the Hawks have identified key pieces of their growing nucleus. Chris Fedor, cleveland.com, "Cleveland Cavaliers and John Beilein’s search for ‘small victories’ that will define the season -- Chris Fedor," 3 July 2019 These are the naturally occurring variations that reflect whether an oxygen atom has six or eight neutrons in its nucleus. Jon Gertner, WIRED, "The Top Secret Cold War Project That Pulled Climate Science From the Ice," 12 June 2019 Three of the committee of eight—Leroy A. Wright, George Marston and Julius Wangenheim -- are alive to see the plan transferred from paper to its nucleus—Civic Center—erected. The San Diego Union, San Diego Union-Tribune, "From the Archives: 1939: ‘Guardian of Water’ dedicated at waterfront," 10 June 2019 Those players must form the nucleus of this team — and not just this year but for years to come. Armando Salguero, miamiherald, "Young players, led by first-round pick Christian Wilkins, delivering small victories to Miami Dolphins," 4 June 2019 Police surrounded the plaza at the central post office that has been a nucleus of the revolt. Washington Post, "Algerians protest, celebrate independence day amid tensions," 5 July 2019 For a Grizz team that has spent several years wedded to an aging nucleus and struggling to come up with a coherent vision of the future, the past two drafts—Jaren Jackson Jr. and now Morant and Clarke—have been a great step toward the latter. Andrew Sharp, SI.com, "2019 NBA Draft Winners and Losers: Grizzlies, Suns, and Two Stories for the Pelicans," 21 June 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

10 Aug 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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