/ ˈnjuːkliəs; NAmE ˈnuː-/ noun ( pl. nu·clei / -kliaɪ; NAmE /)
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.
( biology ) the central part of some cells, containing the genetic material
3.
the central part of sth around which other parts are located or collected :
These paintings will form the nucleus of a new collection.
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WORD ORIGIN
early 18th cent.: from Latin , literally kernel, inner part , diminutive of nux , nuc- nut.