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nucleus medical definition
noun pl. nu·cle·us·es or nu·cle·i
- A large, membrane-bound, usually spherical protoplasmic structure within a living cell, containing the cell's hereditary material and controlling its metabolism, growth, and reproduction. Also called karyon.
- A membraneless structure in microorganisms that contains genetic material but does not itself replicate. Also called nucleoid.
- A group of specialized nerve cells or a localized mass of gray matter in the brain or spinal cord.
- The substance around which a urinary or other calculus forms.
- The positively charged central region of an atom that is composed of protons and neutrons and that contains almost all of the mass of the atom.
- A group of atoms bound in a structure, such as a benzene ring, that is resistant to alteration in chemical reactions.
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