Defined as the fact that the same linguistic segment can lend itself to two mutually exclusive interpretations, true ambiguity should be distinguished from « pluri-equivocality by default » (vague meaning, referential indetermination) and « pluri-equivocality by excess » (the meanings build up without being mutually exclusive). It covers a certain number of cases which can be classed according to different criteria, such as the source of the ambiguity (lexical, morphosyntactic, polycategorical, or pragmatic ambiguities), or the extension of the ambiguous segment. The phenomenon can be envisaged in language (virtual ambiguity), or in discourse (effective ambiguity). If virtual ambiguity is constant, effective ambiguity is more exceptional in...