1 a the central part or thing round which others are collected. b the kernel of an aggregate or mass.
2 an initial part meant to receive additions.
3 Astron. the solid part of a comet's head.
4 Physics the positively charged central core of an atom that contains most of its mass.
5 Biol. a large dense organelle of eukaryotic cells, containing the genetic material.
6 a discrete mass of grey matter in the central nervous system.
Etymology: L, = kernel, inner part, dimin. of nux nucis nut
Useful english dictionary. 2012.