plural nuclei
ˈnuːkliˌaɪ 
also nucleuses
also nucleuses
1
biology
: the central part of most cells that contains genetic material and is enclosed in a membrane
2
physics
: the central part of an atom that is made up of protons and neutrons
3
: a central or most important part of something
—usually + of
players who are the nucleus [=core] of the team
Cite this Entry
“Nucleus.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/nucleus. Accessed 19 Jun. 2026.
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