nucleus

nu·cle·us

noun \ˈnü-klē-əs, ˈnyü-\

plural nu·clei \-klē-ˌī\ also nu·cle·us·es

Definition of NUCLEUS

1

a : the small bright body in the head of a comet

b : the small brighter and denser portion of a galaxy

2

: a central point, group, or mass about which gathering, concentration, or accretion takes place: as

a : a cellular organelle of eukaryotes that is essential to cell functions (as reproduction and protein synthesis), is composed of nucleoplasm and a nucleoprotein-rich network from which chromosomes and nucleoli arise, and is enclosed in a definite membrane — see cell illustration

b : a mass of gray matter or group of cell bodies of neurons in the central nervous system

c : a characteristic and stable complex of atoms or groups in a molecule; especially : ring <the naphthalene nucleus>

d : the positively charged central portion of an atom that comprises nearly all of the atomic mass and that consists of protons and usually neutrons

3

: the peak of sonority in the utterance of a syllable

4

: a basic or essential part : core <players who are the nucleus of the team>

Examples of NUCLEUS

1. <a college campus that was a nucleus of opposition to the war>
2. <the nucleus of the movement's methodology has always been passive resistance>

Origin of NUCLEUS

New Latin, from Latin, kernel, from nuc-, nux nut — more at nut

First Known Use: 1704

Related to NUCLEUS

Synonyms

axis, base, capital, central, core, cynosure, epicenter, eye, focus, ground zero, heart, hub, locus, mecca, navel, nerve center, nexus, center, omphalos, seat

Related Words

headquarters; happy hunting ground, hive, hotbed, hot spot, playground, playland; kernel, nub, pith; deep, thick; essence, quintessence, soul; attraction, lodestone (also loadstone), magnet, polestar

Other Cell Biology Terms

cytology, gamete, vacuole, zygote

nu·cle·us

noun \ˈn(y)ü-klē-əs\   (Medical Dictionary)

plural ; nu·clei \-klē-ˌī\ (audio pronunciation)also ; nu·cle·us·es

Medical Definition of NUCLEUS

1

: a cellular organelle of eukaryotes that is essential to cell functions (as reproduction and protein synthesis), is composed of nuclear sap and a nucleoprotein-rich network from which chromosomes and nucleoli arise, and is enclosed in a definite membrane

2

: a mass of gray matter or group of nerve cells in the central nervous system

3

: a characteristic and stable complex of atoms or groups in a molecule; especially : ring 2 <the naphthalene nucleus>

4

: the positively charged central portion of an atom that comprises nearly all of the atomic mass and that consists of protons and neutrons except in hydrogen which consists of one proton only

Illustration of NUCLEUS