'pbThe present volume wishes to pay tribute to Anne-Claude Berthoud and his career characterised by what is both a research object and an ambition: Act in the diversity of languages.’ br/b Honorary Professor of the University of Lausanne, Anne-Claude Berthoud was responsible for general language chairs and applied from 1982. His scientific and academic background, characterised by generous involvement in teaching pragmatics and language acquisition and by the dynamism of research carried out, puts at the heart of reflection the active force of language, combined with three complementary guidelines: acting in terms of narrative operations, acting in a verbal way and acting more comprehensively in social institutions. In Anne-Claude Berthoud, this paradigm of action is always accompanied by an interest in the diversity of languages, the comparison of which makes it possible to identify the way in which language works in general. Br/b being a unique scientific background, this book shows the changes in the language of the last 40 years, marked by an increasing consideration of the context and the use of language for communication purposes. The chapters of this volume of honour, written by researchers from different backgrounds, address both language theory and description issues (reference, relationship between language, communication and interaction) and issues related to language diversity (acquisition, multilingualism and language policy). They thus provide relevant insights into current language research.’/PB