In 2018 the Council of the ICCA Consortium decided to develop a lexicon of meaningful, and at times complex, concepts and terms frequently used in its work, policies and relations with its Members and Partners. A few specific papers had been commissioned and prepared before, but no attempt had been made to collate working definitions of frequent use, while many felt a need for such a reference compendium. This document is the result of the Council’s decision. It is a rich beginning, expected to evolve and be further integrated and enriched in the years to come. The concepts and terms collated here are relatively few. We thus decided to list them not in alphabetical order but in our suggested order of reading or glancing through (one of the many possible ones).