nucleus
     n 1: a part of the cell containing DNA and RNA and responsible
          for growth and reproduction [syn: {cell nucleus}, {karyon}]
     2: the positively charged dense center of an atom
     3: a small group of indispensable persons or things; "five
        periodicals make up the core of their publishing program"
        [syn: {core}, {core group}]
     4: (astronomy) the center of the head of a comet; consists of
        small solid particles of ice and frozen gas that vaporizes
        on approaching the sun to form the coma and tail
     5: any histologically identifiable mass of neural cell bodies
        in the brain or spinal cord
     [also: {nuclei} (pl)]
Source: WordNet® 2.0

nuclei
     See {nucleus}
Source: WordNet® 2.0