Nucleus - Definition

n 1: a part of the cell containing DNA and RNA and responsible
for growth and reproduction [syn: nucleus, 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, nucleus, 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
6: the central structure of the lens that is surrounded by the
cortex [syn: lens nucleus, nucleus]