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