nucleus
noun
nu·cle·us
| \ ˈnü-klē-əs
, ˈnyü-\
, ˈnyü-\
plural nuclei\ ˈnü-klē-ˌī
, ˈnyü- \
also nucleuses
, ˈnyü- \
also nucleuses
Definition of nucleus
1a
: the small bright body in the head of a comet
b
: the small brighter and denser portion of a galaxy (see galaxy sense 1b)
2
: a central point, group, or mass about which gathering, concentration, or accretion takes place: such as
a
: a cellular organelle of eukaryotes that is essential to cell functions (such 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 (see molecule sense 1)
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