The International Tectonic Lexicon comprises a first selection of important tectonic terms, explains their meaning and suggests equivalents in the six languages of the International Geological Congress: English, French, German, Italian, Russian, and Spanish. This Lexicon has been called a prodrome because it is a preliminary publication, completed with limited funds. It includes what we and our correspondents consider to be first priority terms. We may have omitted important terms, and at the same time may have included terms which, in the opinion of some readers, might not merit inclusion. That is the risk taken by all who edit compilations. We hope that this Lexicon will be a source of information and education for many colleagues in all countries.