noun (n)

• a part of the cell containing DNA and RNA and responsible for growth and reproduction(noun.body)

  Synonym:
  cell nucleus, karyon
  

  source: wordnet30
• the positively charged dense center of an atom(noun.object)

  source: wordnet30
• a small group of indispensable persons or things(noun.group)

  Synonym:
  core, core group
  

  source: wordnet30
• (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(noun.object)

  source: wordnet30
• any histologically identifiable mass of neural cell bodies in the brain or spinal cord(noun.body)

  source: wordnet30
• the central structure of the lens that is surrounded by the cortex(noun.body)

  Synonym:
  lens nucleus
  

  source: wordnet30
• A kernel; hence, a central mass or point about which matter is gathered, or to which accretion is made; the central or material portion; -- used both literally and figuratively.(noun)

  source: webster1913