Book excerpt: The IAEA Safety Glossary defines and explains technical terms used in the IAEA Safety Standards and other safety related IAEA publications, and provides information on their usage. The 2018 Edition of the IAEA Safety Glossary is a new edition of the IAEA Safety Glossary, originally issued in 2007. It has been revised and updated to take into account new terminology and usage in safety standards issued between 2007 and 2018. The revisions and updates reflect developments in the technical areas of application of the safety standards and changes in regulatory approaches in Member States.