The dictionary, a reference work, has a conventional structure which makes it an information retrieval instrument. It functions at two levels: that of headwords, generally ordered from A to Z (macrostructure); and that of entries or articles, giving a set of linguistic information for each headword (microstructure). A dictionary's consultability is measured in terms of the rapidity with which the user is able to find the correct headword in the macrostructure and then the required information in the microstructure. In a modern dictionary the consultability of the microstructure is assisted by a recurrent structure in which, in principle, each headword is always followed by the same types of information, given in the same order and in the same typeface; in which the most frequent pieces of information (";masculine noun";, ";transitive verb";, ";from the Latin";, etc.) are presented in the form of conventional abbreviations (";m.";, ";tr.";, ";Lat.";). Older dictionaries had a less rigorous microstructure and a less predictable content. The aim of the Copulex Project is to analyze in French lexicography the history and evolution (progressive codification) of the systems of copulas giving access to the microstructure by connecting the headword to the different pieces of information (orthography, pronunciation, grammatical category, meaning, use, etymology, etc.) This paper deals with the question of the user's linguistic and dictionary competence, which has to make up for the deficiencies or the implicitness of the system offered by the lexicographer, and examines two specific cases, one from an early dictionary (Trévoux 1743), the other from a modern one (Lexis 1975).