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English definition of “nucleus”

nucleus

noun [C]  /ˈnu·kli·əs/ (plural nuclei  /ˈnu·kliˌɑɪ/) us  
the central part of something People or things that form the nucleus of something are the most important part of it: These two people will form the nucleus of a new management team to promote sales in South America. physics A nucleus is the central part of an atom. biology A nucleus is the central part of a cell that controls its growth.
(Definition of nucleus from the Cambridge Academic Content Dictionary © Cambridge University Press)
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