An essential feature of all languages is that, through their agency, the universe of human experience is being disintegrated (= resolved into elements) and transformed into concepts. There are, consequently, as many universal systems as languages exist. The logical and ontological relations prevailing among concepts may be considered to be relevant criteria for translation. With a view to this and other applications it is desirable that concepts and their relationships be studied and that they be accessible for reference in the form of systematized dictionaries and vocabularies. Technical committee 37 ‘Terminology’ of ISO is concerned with either aspect. This paper discusses the theoretical and practical issues involved.