nucleus
[ noo-klee-uhs, nyoo- ]
/ ˈnu kli əs, ˈnyu- /
noun, plural nu·cle·i [noo-klee-ahy, nyoo-] /ˈnu kliˌaɪ, ˈnyu-/, nu·cle·us·es.
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
Example sentences from the Web for nucleus
British Dictionary definitions for nucleus
nucleus
/ (ˈnjuːklɪəs) /
noun plural -clei (-klɪˌaɪ) or -cleuses
Word Origin for nucleus
C18: from Latin: kernel, from
nux nut
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.
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.
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.