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

Keep scrolling for more

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

Better known in Arabic as a Masjid, the mosque represents the nucleus of the Muslim family and community. chicagotribune.com, "Mosque to open in building that previously housed a VFW post in Skokie," 12 Aug. 2019 The physician, operating as the nucleus of a large surgical team, conducts about 95 percent of heart transplant surgeries at Supizio Cardiovascular Center, the university’s new heart hospital that opened in 2011. Paul Sisson, San Diego Union-Tribune, "UCSD heart transplant program posts nation’s best one-year-survival rates," 8 Aug. 2019 Led by a veteran, accomplished nucleus that includes Eugenie Le Sommer, Amandine Henry and Wendie Renard, France is one of the favorites to win it all. Avi Creditor, SI.com, "LIVE: France Hosts South Korea to Open 2019 Women's World Cup," 7 June 2019 While the nucleus of one of our cells contains about 30,000 genes, our mitochondria contain just 37 genes. Radhika Viswanathan, Vox, "3 biological parents, 1 child, and an international controversy," 24 July 2018 The light arose from the collision between a remarkably energetic neutrino – a wraithlike subatomic particle moving close to the speed of light – and the nucleus of a hydrogen or oxygen atom deep within the ice. Eoin O'carroll, The Christian Science Monitor, "Neutrino demonstration heralds a new way of observing the cosmos," 12 July 2018 Political observers often wondered whether Jordan’s political influence extended much beyond that conservative nucleus which appreciates his rabble-rousing maneuvers. Chad Pergram, Fox News, "Jim Jordan, facing accusations of ignoring sexual abuse, faces political crisis," 7 July 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 That deft disappearing act forms the nucleus of Los Angeles artist Katherine Gray’s conceptual installations. R. Daniel Foster, latimes.com, "Vanishing act: Katherine Gray’s explorations in glass and light," 28 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.

See More

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

Keep scrolling for more

Learn More about nucleus

Statistics for nucleus

Last Updated

24 Aug 2019

Look-up Popularity

Time Traveler for nucleus

The first known use of nucleus was in 1668

See more words from the same year

Keep scrolling for more

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

Keep scrolling for more

Comments on nucleus

What made you want to look up nucleus? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

concealment of treason or felony

Get Word of the Day daily email!

Test Your Vocabulary

The Exceptions Quiz III

  • one green toy robot amidst many red toy robots
  • Which of these words does not mean "nonsense"?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!