Since the last edition of the IAEA Safeguards Glossary, IAEA safeguards implementation has continued to evolve, with a greater emphasis on ‘State as a whole’ considerations in the development of State level safeguards approaches. This new edition reflects these developments and represents terms that are specific and unique to IAEA safeguards. Since the last edition of the IAEA Safeguards Glossary in 2001, IAEA safeguards implementation has continued to evolve, with a greater emphasis on 'State as a whole' considerations in the development of State level safeguards approaches, and reflecting a myriad of technological advancements. This new edition reflects these developments and represents terms that are either specific and unique to IAEA safeguards, or those that may be used in other domains, but which have a specific meaning or application relevant to IAEA safeguards. New terms that have come into common use over the past two decades have also been introduced. Each term includes a definition, and where applicable, further explanation or examples. Each section addresses a specific subject area relevant to IAEA safeguards, and the terms are arranged in relation to the subject area. Within each definition, terms that are defined elsewhere in the Glossary are italicized and an index referring to the term numbers has been provided for ease of reference. The terms have been translated into the official languages of the IAEA, as well as into German and Japanese.