nucleus nucleus /ˈnuːkliːəs/

noun

1. () A part of the cell containing DNA and RNA and responsible for growth and reproduction  ( cell nucleus , karyon , nucleus )
   a part of the cell containing DNA and RNA and responsible for growth and reproduction
     The nucleus contains the genetic material and controls the activities of the cell.
   The nucleus contains the genetic material and controls the activities of the cell.
   
2. () A small group of indispensable persons or things  ( core group , nucleus , core )
   a small group of indispensable persons or things
    Five periodicals make up the core of their publishing program
   five periodicals make up the core of their publishing program
   
   
3. () The positively charged dense center of an atom  ( nucleus )
   the positively charged dense center of an atom
     Within the cell, the nucleus contained the genetic information that governed its functions.
   Within the cell, the nucleus contained the genetic information that governed its functions.
   
4. The central structure of the lens that is surrounded by the cortex  ( lens nucleus , nucleus )
   the central structure of the lens that is surrounded by the cortex
   
5. Any histologically identifiable mass of neural cell bodies in the brain or spinal cord  ( nucleus )
   any histologically identifiable mass of neural cell bodies in the brain or spinal cord
   
6. (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 )
   (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