nucleus

noun

brain structure consisting of a relatively compact cluster of neurons
the small bright body in the head of a comet
the small brighter and denser portion of a galaxy
a central point, group, or mass about which gathering, concentration, or accretion takes place
a cellular organelle of eukaryotes that is essential to cell functions (such as reproduction and protein synthesis), is composed of nucleoplasm and a nucleoprotein-rich network from which chromosomes and nucleoli arise, and is enclosed in a definite membrane
center of an atom