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

The development’s nucleus of housing, businesses, and shops would be balanced by a European-style public plaza and several parks, with 21 percent of the site set aside for green space. Jay Walljasper, WIRED, "The Bitter Battle to Turn an Old Factory Into a 21st Century 'Eco-Village'," 3 July 2018 After its conclusion, Garber stood in the gym, the nucleus of the building’s medical advancements, and cited it as an example of growth in the league. Sam Mcdowell, kansascity, "MLS commissioner on Sporting KC: ‘The model for Major League Soccer is right here’ | The Kansas City Star," 19 May 2018 The design that caught her eye looks like a fish scale or fan, and became the nucleus for Bulgari's 2013 Divas' Dream collection. Alice B-b, A-LIST, "No Place Like Rome," 4 July 2018 Those reasons included an affinity for head coach Rick Tocchet and his style of play, the Coyotes’ young nucleus of players, as well as Arizona being an attractive climate in which to live. Richard Morin, azcentral, "Arizona Coyotes' improved reputation among 5 observations after the opening of free agency," 2 July 2018 Up-down quark matter would definitively rule out the doomsday scenario: It should be positively charged and repel atomic nuclei. Adrian Cho, Science | AAAS, "Weird new form of nuclear matter might lie just beyond experimenters' grasp," 15 May 2018 The engines that power it are named after New Zealand’s most famous physicist, Lord Rutherford, who discovered the atomic nucleus and much else. The Economist, "Is New Zealand the world’s best rocket-launching site?," 5 Apr. 2018 Markarian 266's beauty belies the chaos the centers of the colliding galaxies, where each contains an active galactic nucleus where gas and debris is being funneled into a supermassive black hole. David Grossman, Popular Mechanics, "Gorgeous Hubble Shot Captures Colliding Galaxies," 14 Dec. 2017 Moving forward, the researchers hope to sequence a genome from the ancient panda’s nuclear DNA, which is found in the nucleus of a cell. Brigit Katz, Smithsonian, "This Ancient Panda Skull Belongs to a Previously Unknown Lineage," 20 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

5 Oct 2018

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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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