Nucleus

Nucleus may refer to:

In science:
 * Atomic nucleus, the collection of protons and neutrons in the center of an atom that carries the bulk of the atom's mass and positive charge
 * Cell nucleus, is a small spherical structure in a cell which contains the cell's DNA and is the control center of the cell
 * Nucleus (neuroanatomy), a central nervous system structure composed mainly of gray matter

In linguistics:
 * Syllable nucleus, the central part of a syllable
 * Sentence nucleus, the syllable which receives the greatest stress in a word