nucleus - definition and synonyms

 
noun [countable] 

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/ˈnjuːkliəs/
singularnucleus
pluralnuclei
  1. 1
    the central or basic part of something
    nucleus of:

    These two groups formed the nucleus of a new political party.

  2. 2
    chemistry the central part of an atom, consisting of protons and neutrons
    1. a.
      the part of a cell that contains the chromosomes