Les notions linguistiques de figement et de contrainte

Summary The paper addresses the question of how the notion of fixed expression or idiom has to be defined. Usually idioms are defined as expressions which are characterized by semantic opacity, lack of lexical (paradigmatic) variation and morphosyntactic constraints. However, so-called ‘free’ (i.e. non idiomatic) expressions can be shown to bear similar lexical and morphosyntactic constraints, so that the limit between ‘fixed’ and ‘free’ expressions is much less clear-cut than one would expect. The only real difference which opposes idioms from ‘non-idioms’ is semantic opacity. This theoretical problem is illustrated in the paper by a case study of regional French expressions belonging either to Quebec French, Belgian French, Swiss French or French from France. The latter research is part of a large project (BFQS-project) which aims at the recollection and syntactic description of all French idiomatic expressions used in Europe and/or North-America.