either of two isomeric hydroxyl derivatives, C 1 0 H 7 OH, of naphthalene (alpha-naphthol or 1-naphthol and beta-naphthol or 2-naphthol) white or yellowish crystals, with a phenolic odor, that darken on exposure to light: used chiefly in dyes, drugs, perfumes, and insecticides.
