This second edition of IUPAC's 'gold' book represents a very substantial enhancement of the first. In the ten years since the first edition was published, IUPAC has revised and updated most of the original definitions, and produced new glossaries of terms in many areas of chemistry not previously covered. These include stereochemistry, photochemistry, organic class names, atmospheric chemistry, catalysis, biotechnology, chromatography, toxicology and bioanalytical chemistry. The resulting compendium, like the first edition, contains only definitions approved by international consensus and thus can be regarded as truly authoritative.