Naph"thol (?), n. [Naphthalene + -ol.] (Chem.) Any one of a series of hydroxyl derivatives of naphthalene, analogous to phenol. In general they are crystalline substances with a phenol (carbolic) odor.

Naphthol blue, Naphthol orange, Naphthol yellow(Chem.), brilliant dyestuffs produced from certain complex nitrogenous derivatives of naphthol or naphthoquinone.