The IUPAC ( International Union of Pure and Applied Chemistry) nomenclature is a system of naming chemical compounds and for describing the science of chemistry in general. The rules for naming organic and inorganic compounds are printed in two publications, the Blue Book and the Red Book . A third publication, Green Book, contains recommendations for the use of symbols for physical quantities (in association with the IUPAP), while a fourth, the Gold Book, definies a large number of technical terms used in chemistry.