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.
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.
- 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. 2023
How to use nucleus in a sentence
Having no electric charge, the neutron was the ideal bullet to shoot into an atom, able to penetrate the nucleus and destabilize it.How understanding nature made the atomic bomb inevitable | Tom Siegfried | August 6, 2020 | Science News
In an atom, the protons and neutrons hang out in the center, or nucleus.
The familiar protons and neutrons that make up the atomic nucleus are examples of baryons.CERN: Physicists Report the Discovery of Unique New Particle | Harry Cliff | July 15, 2020 | Singularity Hub
Those energy-producing organelles are inherited from a mother and have their own DNA, distinct from the genetic information — from both parents — that’s stored in a cell’s nucleus.A bacterial toxin enables the first mitochondrial gene editor | Jack J. Lee | July 13, 2020 | Science News
Alternatively, the detector might contain a minute amount of tritium, a radioactive form of hydrogen with two neutrons in its nucleus.An unexpected result from a dark matter experiment may signal new particles | Emily Conover | June 17, 2020 | Science News
Deuterium is an isotope of hydrogen containing a proton and neutron in its nucleus, while normal hydrogen has only a proton.
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 | THE DAILY BEAST
To win you have to start winning and these very attractive candidates could help form a nucleus to rebuild the Party.
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 | THE 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 | THE DAILY BEAST
Any epithelial cell may be so granular from degenerative changes that the nucleus is obscured.
Each contains one irregular nucleus or several small, rounded nuclei.
Occasionally the nucleus is irregular in shape, "clover-leaf" forms being not infrequent.
Wright's stain gives the nucleus a deep purple color and the cytoplasm a pale robin's-egg blue in typical cells.
Each contains a single round or oval nucleus, often located eccentrically.
British Dictionary definitions for nucleus
a central or fundamental part or thing around which others are grouped; core
a centre of growth or development; basis; kernel: the 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 reactions: the benzene nucleus
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
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
Scientific definitions for nucleus
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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Cultural definitions for nucleus (1 of 2)
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.