The core, central part of something, around which other elements are assembled. / An initial part or version that will receive additions.

(physics) An atomic nucleus comprising three bound components in which any subsystem of two components is unbound.

(physics) An atomic nucleus whose radius is appreciably larger than that predicted by the liquid drop model (wherein the nucleus is assumed to be a sphere of constant density).

(anatomy) A cluster of neurons, in each hemisphere of the cerebellum, that links it with the rest of the brain.

Either of two pairs of structures situated on the lower surface of the thalamus that relay sensory impulses to the cortex, the lateral geniculate nucleus, which relays visual impulses, and the medial geniculate nucleus, which relays auditory impulses.

(neuroanatomy) Any of four nuclei in the medulla oblongata on each side of the floor of the fourth ventricle of the brain in which fibers of the vestibular nerve terminate.

(physics) A nucleus of an atom; consisting of protons and neutrons, surrounded by an electron cloud.

A dopaminergic nucleus found near the most anterior portion of the caudate nucleus. / The primary nucleus thought to be involved with addiction

A collection of cells in the tegmentum involved in movement. / Specifically, the title nucleus involved in the rubrospinal movement pathway.

a small atmospheric particle, around which an ice crystal grows