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

Progeria is caused by a mutation in a gene that regulates production of a protein that helps shape and support the nucleus of cells throughout the body. Washington Post, "Kids with rare rapid-aging disease get hope from study drug," 24 Apr. 2018 The vast majority of our DNA—the chromosomes in the nucleus of each cell—is just what you’d expect: a mix of genetic material from both mother and father. Cathleen O'grady, Ars Technica, "Plot twist: Mitochondrial DNA can come from both parents," 28 Nov. 2018 Others credit the Bedouin tribes on Saudi Arabia’s Nejd plateau as the nucleus of breeders from which the horses arose. Peter Gwin, WSJ, "The Horses That Changed History," 19 June 2018 To picture a chemical bond, imagine an atom as a tiny nucleus immersed in a giant diffuse cloud that is its electrons. Sophia Chen, WIRED, "Chemists Orchestrate the Molecular Union of Two Single Atoms," 27 Apr. 2018 Numerous other challenges face the attorneys who will work alongside Sekulow and counsel Ty Cobb - who have functioned as Trump's legal nucleus for weeks following the resignation of John Dowd, a legal veteran and the team's former leader. The Washington Post, OregonLive.com, "She wore a dinosaur puppet during a military oath. It got her and a colonel removed from the job," 19 Apr. 2018 For the thread, Diane chose Namjoon as the nucleus; Jin as the endoplasmic recticulum; Yoongi as the cell membrane; Hoseok as the mitochondria; Jimin as the Golgi body; Taehyung as the lysosome; and Jungkook for the ribosome. Lauren Rearick, Teen Vogue, "A BTS Fan Went Viral After Comparing Members of the Group to an Animal Cell," 23 Nov. 2018 Whether another championship nucleus is hiding in plain sight will reveal itself over time. Larry Stone, The Seattle Times, "Loss to Broncos shows Seahawks fans should brace themselves for a rollercoaster season," 10 Sep. 2018 These particles, primarily composed of electrons, protons, and helium nuclei (known as alpha particles), fly all over the solar system. Jay Bennett, Popular Mechanics, "The New Science of the Sun Will Be Astounding—And Possibly Terrifying," 9 Aug. 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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Statistics for nucleus

Last Updated

20 Apr 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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