Controlled vocabularies of information languages show a variety of practices. There are varied applications of the same language, two. Common problems are reflected by them, although the theoretical framework of controlled vocabularies can differ. In spite of the differences of information languages, language groups and their applications, they share common features, because they are originated by human activities, involving thinking and speaking. Dominating patterns of a specific information thesaurus are primarily determined by the interaction of the conceptual and linguistic levels. In controlled vocabularies, specific patterns and models can be formed in multiple ways in connection with editing methods; they can be 'inherited' from natural language use, they can derive from the interconnection of conceptual and linguistic levels, or they are determined by the principle of general interdependence. Comparing representative examples of information languages based on different natural languages, and listing selected examples from Hungarian public libraries, the study focuses on the common difficulties of applications that concern the use of information languages in general.