Definition of nuclei:
(n) :
(chemistry, physics) The massive, positively charged central part of an atom, made up of protons and neutrons.
(n) :
(cytology) A large membrane-enclosed organelle found in eukaryotic cells which contains genetic material.
(n) :
The core, central part of something, around which other elements are assembled.
(n) :
An initial part or version that will receive additions.
(n) :
(neuroanatomy) A ganglion, cluster of many neuronal bodies where synapsing occurs.
(n) :
(phonetics, phonology) The central part of a syllable, most commonly a vowel.