nucleus

[ noo-klee-uhs, nyoo- ]

/ ˈnu kli əs, ˈnyu- /

SEE MORE SYNONYMS FOR nucleus ON THESAURUS.COM

noun, plural nu·cle·i [noo-klee-ahy, nyoo-] /ˈnu kliˌaɪ, ˈnyu-/, nu·cle·us·es.

a central part about which other parts are grouped or gathered; core: A few faithful friends formed the nucleus of the club.

Biology. a specialized, usually spherical mass of protoplasm encased in a double membrane, and found in most living eukaryotic cells, directing their growth, metabolism, and reproduction, and functioning in the transmission of genic characters.

Physics. the positively charged mass within an atom, composed of neutrons and protons, and possessing most of the mass but occupying only a small fraction of the volume of the atom.

Anatomy. a mass of nerve cells in the brain or spinal cord in which nerve fibers form connections.

Also called condensation nucleus. Meteorology. a particle upon which condensation of water vapor occurs to form water drops or ice crystals.

Chemistry. a fundamental arrangement of atoms, as the benzene ring, that may occur in many compounds by substitution of atoms without a change in structure.

Astronomy. the condensed portion of the head of a comet.

Phonetics.

the central, most prominent segment in a syllable, consisting of a vowel, diphthong, or vowellike consonant, as the a-sound in cat or the l-sound in bottled; peak.
the most prominent syllable in an utterance or stress group; tonic syllable.

Nearby words

nucleotidase, nucleotide, nucleotides, nucleotidyltransferase, nucleotoxin, nucleus, nucleus fastigii, nucleus gracilis, nucleus of solitary tract, nuclide, nuddy

Origin of nucleus

1695–1705; < Latin: kernel, syncopated variant of nuculeus, equivalent to nucu(la) little nut (nuc-, stem of nux nut + -ula -ule) + -leus noun suffix

SYNONYMS FOR nucleus

1 center, kernel, heart.

SEE MORE SYNONYMS FOR nucleus ON THESAURUS.COM

Related forms

sub·nu·cle·us, noun, plural sub·nu·cle·i, sub·nu·cle·us·es.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for nucleus

Deuterium is an isotope of hydrogen containing a proton and neutron in its nucleus, while normal hydrogen has only a proton.
Are Comets the Origin of Earth’s Oceans?|Matthew R. Francis|December 14, 2014|DAILY BEAST
A July 1884 New York Times article called her “the nucleus and center of the whole organization of crime in New York City.”
Meet 'The Queen of Thieves' Marm Mandelbaum, New York City's First Mob Boss|J. North Conway|September 7, 2014|DAILY BEAST
To win you have to start winning and these very attractive candidates could help form a nucleus to rebuild the Party.
The GOP’s Long, Hard Road in California|Stuart Stevens|May 8, 2014|DAILY BEAST
The Russian people should form the state at the center, “a nucleus around which other peoples are gathered.”
Putin’s Dream of Empire Doesn’t Stop at Crimea, Or Even Ukraine|Oleg Shynkarenko|March 23, 2014|DAILY BEAST

To me, the nucleus of Peter Parker is him being left behind by his parents.
Marc Webb Takes Us Inside ‘The Amazing Spider-Man 2’ and Discusses His Rise to the A-List|Marlow Stern|March 15, 2014|DAILY BEAST
"It is going to be what they call a nucleus," said Olive, showing a little piece of fancy work.
The Captain's Toll-Gate|Frank R. Stockton
Toward the centre of the cell, especially if it has first been treated with iodine, the nucleus may be found.
Elements of Structural and Systematic Botany|Douglas Houghton Campbell
He set out with the Cherethites and Pelethites, who were to form the nucleus of the army which he hoped to collect on the way.
History of the Jews, Vol. I (of 6)|Heinrich Graetz
Their successors composed the nucleus of the party of Cushing, Everett, and Winthrop in 1860.
Expansion and Conflict|William E. Dodd
The nucleus of a branch exhibition was forming itself in Welbeck Street.
The Crime Doctor|Ernest William Hornung

British Dictionary definitions for nucleus

nucleus

/ (ˈnjuːklɪəs) /

noun plural -clei (-klɪˌaɪ) or -cleuses

a central or fundamental part or thing around which others are grouped; core

a centre of growth or development; basis; kernelthe nucleus of an idea

biology (in the cells of eukaryotes) a large compartment, bounded by a double membrane, that contains the chromosomes and associated molecules and controls the characteristics and growth of the cell

anatomy any of various groups of nerve cells in the central nervous system

astronomy the central portion in the head of a comet, consisting of small solid particles of ice and frozen gases, which vaporize on approaching the sun to form the coma and tail

physics the positively charged dense region at the centre of an atom, composed of protons and neutrons, about which electrons orbit

chem a fundamental group of atoms in a molecule serving as the base structure for related compounds and remaining unchanged during most chemical reactionsthe benzene nucleus

botany

the central point of a starch granule
a rare name for nucellus

phonetics the most sonorous part of a syllable, usually consisting of a vowel or frictionless continuant

logic the largest individual that is a mereological part of every member of a given class

Word Origin for nucleus

C18: from Latin: kernel, from nux nut

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for nucleus

nucleus

[ nōō′klē-əs ]

n. pl. nu•cle•us•es

A large, membrane-bound, usually spherical protoplasmic structure within a living cell, containing the cell's hereditary material and controlling its metabolism, growth, and reproduction.karyon

A membraneless structure in microorganisms that contains genetic material but does not itself replicate.nucleoid

A group of specialized nerve cells or a localized mass of gray matter in the brain or spinal cord.

The substance around which a urinary or other calculus forms.

The positively charged central region of an atom that is composed of protons and neutrons and that contains almost all of the mass of the atom.

A group of atoms bound in a structure, such as a benzene ring, that is resistant to alteration in chemical reactions.

Science definitions for nucleus

nucleus

[ nōō′klē-əs ]

Plural nuclei (nōō′klē-ī′)

The positively charged central region of an atom, composed of one or more protons and (for all atoms except hydrogen) one or more neutrons, containing most of the mass of the atom. The strong force binds the protons and neutrons, also known as nucleons, to each other, overcoming the mutual repulsion of the positively charged protons. In nuclei with many nucleons, however, the forces of repulsion may overcome the strong force, and the nucleus breaks apart in the process of radioactive decay. The protons and neutrons are arranged in the nucleus in energy levels known as shells analogous to those of the electrons orbiting the nucleus. The number of protons in the nucleus determines the atom's atomic number and its position in the Periodic Table. See more at atom.

An organelle in the cytoplasm of eukaryotic cells (all cells except prokaryotes) that contains nearly all the cell's DNA and controls its metabolism, growth, and reproduction. The nucleus is surrounded by a pair of membranes called the nuclear envelope, which can be continuous in places with the membranes of the endoplasmic reticulum. The membranes of the nuclear envelope have interconnected pores that allow the exchange of substances with the cell's cytoplasm. The nuclear DNA is wrapped around proteins (called histones) in strands of chromatin, which exists in a matrix known as nucleoplasm (analogous to the cytoplasm outside the nucleus). Just prior to cell division, the chromatin condenses into individual chromosomes, which contain the cell's hereditary information. The nucleus also contains at least one spherical nucleolus, which mainly contains RNA and proteins and directs the construction of the cell's ribosomes. See more at cell.

The solid central part of a comet, typically several kilometers in diameter and composed of ice, frozen gases, and embedded chunks of rock and dust. It is the permanent part of a comet from which the coma and tail are generated as the comet approaches the Sun. See more at comet.
See galactic nucleus.

Culture definitions for nucleus (1 of 2)

nucleus

plur. nuclei (nooh-klee-eye)

The small, dense center of the atom. The nucleus is composed of protons and neutrons and has a positive electrical charge.

Note

Nuclear physics deals with the composition and structure of the nucleus.

Culture definitions for nucleus (2 of 2)

nucleus

plur. nuclei

In biology, the central region of the cell, in which DNA is stored. The nucleus usually appears as a dark spot in the interior of the cell. Primitive cells (such as bacteria and blue-green algae) have no nuclei.