Definition of: vitamin

(vī′tə·min) noun Biochem.
Any of a group of complex organic substances found in minute quantities in most natural food-stuffs, and closely associated with the maintenance of normal physiological functions in man and animals. Numerous forms have been isolated and described under special names. Also vi′ta·mine (-mēn, -min). [<L vita life + AMINE]
—vi′ta·min′ic adjective