[nu.cle.us] n, pl nu.clei also nu.cle.us.es [NL, fr. L, kernel, dim. of nuc-, nux nut--more at nut] (1704) 1: the small brighter and denser portion of a galaxy or of the head of a comet
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 nuclear sap 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 nerve cells in the central nervous system c: a characteristic and stable complex of atoms or groups in a molecule; esp: ring "the naphthalene ~" d: 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
3: the peak of sonority in the utterance of a syllable