The four-year RDA Toolkit Restructure and Redesign Project included a major expansion of the standard to align RDA: Resource Description and Access with the IFLA Library Reference Model, which is the conceptual basis of RDA. This expansion included the addition of several new entities and hundreds of new elements. The RDA Glossary features the complete terminology for RDA as it was constituted for the 15 December 2020 release to the RDA Toolkit. It includes: – an alphabetical listing of all RDA entities, elements, vocabulary terms and other RDA-related terms – a label and definition for all entries and, where needed, a scope note, inverses and cross-references – two indexes: an RDA Elements Index, which organizes RDA elements by their domain entities to give users an idea of the structure of RDA, and an RDA Controlled Vocabularies Index, which is organized by element. Developed and maintained by the RDA Steering Committee (RSC) as part of its oversight of the standard, this glossary will be a useful tool for both training and daily reference for students, instructors and cataloguers.