nucleus

noun
nu·​cle·​us | \ ˈnü-klē-əs How to pronounce nucleus (audio) , ˈnyü- \
plural nuclei\ ˈnü-​klē-​ˌī How to pronounce nucleus (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 the attractive force between negative and positive keeps the smaller-sized electrons grounded within the area surrounding the nucleus, electrons in orbits farther away don't experience the same attractive pull. Miriam Fauzia, USA TODAY, "Fact check: Bending an electrical wire won't stop flow of electricity," 6 Apr. 2021 The coma, or dust envelope that surrounds the comet's nucleus, actually contains compact pebbles, or millimeter-sized grains. Ashley Strickland, CNN, "Pristine interstellar comet came from a system containing giant planets," 30 Mar. 2021 Going back to the 1930s, when they were invented to investigate the structure of the atomic core, or nucleus, these facilities have been used for a range of research purposes. Andrea Willige, Forbes, "Particle Accelerators That Clean Power Plants – And A Lot More," 18 Mar. 2021 But the real intrigue with Grant is the young nucleus coming up in the class of 2023. oregonlive, "PIL football recruiting stock watch: Jefferson’s Trejon Williams looks elite; 2023 Grant duo rising quickly," 17 Mar. 2021 Now, instead of identifying powdered sugar or bacon, their system would take a microscope slide of a urinary cell and identify and measure its nucleus. James Somers, The New Yorker, "The Pastry A.I. That Learned to Fight Cancer," 18 Mar. 2021 An oxygen atom in water is just an oxygen atom, but hydrogen comes in two forms: ordinary hydrogen (with a single proton in its nucleus) and deuterium (with a proton and a neutron). Jeffrey Kluger, Time, "Mars Has Much More Water Than Previously Known—But There's a Catch," 16 Mar. 2021 Since the 19th century, scholars have held that Deuteronomy (or its nucleus of laws) was that book, which in fact had been composed shortly beforehand to justify the centralization of worship at the Temple and other priestly reforms. Jennifer Schuessler, New York Times, "Is a Long-Dismissed Forgery Actually the Oldest Known Biblical Manuscript?," 10 Mar. 2021 Other members came and went, and the group’s name changed from the Teenagers to the Wailing Rudeboys to the Wailing Wailers, but Marley, Tosh and Mr. Wailer were the nucleus. Washington Post, "Bunny Wailer, one of the founders of reggae music, dies at 73," 3 Mar. 2021

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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Time Traveler for nucleus

Time Traveler

The first known use of nucleus was in 1668

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Statistics for nucleus

Last Updated

12 Apr 2021

Cite this Entry

“Nucleus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/nucleus. Accessed 14 Apr. 2021.

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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 nucleus (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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Comments on nucleus

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