American English

Definition of nucleus noun from the Oxford Advanced American Dictionary



    (pl. nuclei
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  1. 1(physics) the part of an atom that contains most of its mass and that carries a positive electric charge see also neutron, proton
  2. 2(biology) the central part of some cells, containing the genetic material
  3. 3the central part of something, around which other parts are located or collected These paintings will form the nucleus of a new collection.
See the Oxford Advanced Learner's Dictionary entry: nucleus