This glossary updates and expands on previous glossaries of toxicological terms provided by IUPAC. Toxicology has become crucial to global trade in chemicals as legislation has become harmonised around the world and is based on the classification of toxicity. This glossary addresses the need for harmonised terminology, especially as toxicology uses terminology from chemistry, medicine, geology, botany, zoology, ecology, and veterinary medicine, as well as some legal terms. This will be a valuable reference for students and researchers in toxicology, those involved in chemicals legislation and regulation and risk assessment.