nucleus, cell nucleus, karyon -- (a part of the cell containing DNA and RNA and responsible for growth and reproduction)
nucleus -- (the positively charged dense center of an atom)
core, nucleus, core group -- (a small group of indispensable persons or things; "five periodicals make up the core of their publishing program")
nucleus -- ((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)
nucleus -- (any histologically identifiable mass of neural cell bodies in the brain or spinal cord)
lens nucleus, nucleus -- (the central structure of the lens that is surrounded by the cortex)
(Sound)
