Other forms: nuclei
A nucleus is the dense centre of an atom, or the control room of a cell. The atomic nucleus, the cell nucleus, a nucleus of supporters.
In an atom it holds the protons and neutrons and nearly all the mass, in a volume so small that an atom is mostly empty space. In a cell it holds the DNA. Figuratively it means the small central group something grows around: a nucleus of volunteers. Note the plural nuclei; nuclear; and that the Latin means a kernel.
1nounnucleusThe dense centre of an atom or a cell.
“The nucleus holds about ninety-nine per cent of the mass.”
2nounsmallA small central group something grows around.
“A small nucleus of volunteers started the charity, which now has thousands of members.”
nucleus is a centre.
Latin nucleus means a kernel, a diminutive of nux, a nut. Nucleus was first used of a comet's head and a seed's kernel, and the atomic sense came in 1844.
Latin
nucleus
English, today
nucleus
Learned borrowing from Latin nucleus. Latin nucleus (“kernel, core”). The earliest uses refer to the head of a comet and the kernel of a seed, both recorded in Lexicon Technicum in 1704. The sense in atomic physics was coined by Q8750 in 1844 in a theoretical meaning.
Etymology from Wiktionary, CC BY-SA