|—n , pl -clei, -cleuses|
|1.||a central or fundamental part or thing around which others are grouped; core|
|2.||a centre of growth or development; basis; kernel: the nucleus of an idea|
|3.||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|
|4.||anatomy any of various groups of nerve cells in the central nervous system|
|5.||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|
|6.||physics the positively charged dense region at the centre of an atom, composed of protons and neutrons, about which electrons orbit|
|7.||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|
|a. the central point of a starch granule|
|b. a rare name for nucellus|
|9.||phonetics the most sonorous part of a syllable, usually consisting of a vowel or frictionless continuant|
|10.||logic the largest individual that is a mereological part of every member of a given class|
|[C18: from Latin: kernel, from nux nut]|
nucleus nu·cle·us (nōō'klē-əs, nyōō'-)
n. pl. nu·cle·us·es or nu·cle·i (-klē-ī')
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. Also called karyon.
A membraneless structure in microorganisms that contains genetic material but does not itself replicate. Also called 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.
|nucleus (n'klē-əs) Pronunciation Key
Plural nuclei (n'klē-ī')