Pronunciation: (lak'tōs),[key] —n. 1. Biochem.a disaccharide, C12H22O11, present in milk, that upon hydrolysis yields glucose and galactose.
2. a white, crystalline, sweet, water-soluble commercial form of this compound, obtained from whey and used in infant feedings, in confections and other foods, in bacteriological media, and in pharmacology as a diluent and excipient. Also called milk sugar, sugar of milk.