1. A part of the cell containing DNA and RNA and responsible for growth and reproduction
   "The cell nucleus is often called the 'control centre' of the cell";
   - cell nucleus, karyon
    
2. The positively charged dense centre of an atom
   "The nucleus contains protons and neutrons"
    
3. A small group of indispensable persons or things
   "five periodicals make up the nucleus of their publishing program";
   - core, core group
    
4. (astronomy) the centre 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
   "As the comet approached the sun, its nucleus began to heat up and release gas"
    
5. Any histologically identifiable mass of neural cell bodies in the brain or spinal cord
   "The thalamus contains several important nuclei"
    
6. The central structure of the lens that is surrounded by the cortex
   "The lens nucleus becomes denser with age, contributing to presbyopia";
   - lens nucleus

Derived forms: nuclei

Type of: anatomical structure, bodily structure, body structure, cell organ, cell organelle, center [US], centre [Brit, Cdn], complex body part, midpoint, neural structure, organelle, set, structure

Part of: atom, cell, comet

Encyclopedia: Nucleus, the Nuclear and Caithness Archives