This volume comprises contributions originally presented at the 15th European Symposium on Languages for Special Purposes held at the University of Bergamo on 29 August - 2 September 2005. The volume is divided into four parts: Approaches to Terminological Theories; Terms in Discourse; Knowledge Elicitation, Ordering and Management; Term extraction and terminographical work. The research presented in the various contributions to this volume clearly indicates that terminology as an inter- and transdisciplinary field of knowledge is firmly developing its theoretical foundations and practical applications in accordance with and within the framework of its overall goal: to ensure and to augment the quality of communication with professional content.