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nucleus

nu·cle·us

nucleus

pronunciation:
nu kli s
features:
Word Explorer
part of speech: noun
inflections: nuclei, nucleuses
definition 1: the central, essential, or highly concentrated part around which other parts are grouped.
The harbor became the nucleus of a booming city.
synonyms:
core, hub
similar words:
center, heart, kernel, marrow, navel, nub, pith, soul
definition 2: in biology, the part of a cell that controls growth and reproduction.
definition 3: the main or central part of something with potential for further growth and development; kernel.
synonyms:
kernel
similar words:
core, embryo, germ, seed
definition 4: the positively charged central part of an atom.
In fission, the nucleus splits into smaller parts, releasing a great deal of energy.
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  cell, physics