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nucleus
[ noo-klee-uhs, nyoo- ]
/ ˈnu kli əs, ˈnyu- /
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noun, plural nu·cle·i [noo-klee-ahy, nyoo-], /ˈnu kliˌaɪ, ˈnyu-/, nu·cle·us·es.
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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
OTHER WORDS FROM nucleus
sub·nu·cle·us, noun, plural sub·nu·cle·i, sub·nu·cle·us·es.Words nearby nucleus
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021
How to use nucleus in a sentence
British Dictionary definitions for nucleus
nucleus
/ (ˈnjuːklɪəs) /
noun plural -clei (-klɪˌaɪ) or -cleuses
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
Medical 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.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Scientific 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.
The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Cultural 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.
notes for nucleus
Nuclear physics deals with the composition and structure of the nucleus.
Cultural 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.
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.