β-lactose

{{Chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 477497006 | Name = Lactose | ImageFile_Ref = | ImageFile = Beta-D-Lactose.svg | ImageSize = 200px | ImageClass = skin-invert-image | IUPACName = β--Galactopyranosyl-(1→4)-α--glucopyranose 4-O-β--Galactopyranosyl-α--glucopyranose | SystematicName = (2R,3R,4S,5R,6S)-2-(Hydroxymethyl)-6-{[(2R,3S,4R,5R,6R)-4,5,6-trihydroxy-2-(hydroxymethyl)oxan-3-yl]oxy}oxane-3,4,5-triol | OtherNames = Milk sugarLactobiose4-O-β-D-Galactopyranosyl-D-glucose | Section1 = | Section2 = | Section4 = | Section7 = }}

Lactose is a disaccharide composed of galactose and glucose and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from (gen. ), the Latin word for milk, plus the suffix -ose used to name sugars. The compound is a white, water-soluble, non-hygroscopic solid with a mildly sweet taste. It is used in the food industry.