The thesis deals with lexical acquisitions in French as a foreign and second language and more particularly with the notion and the role of lexical error as an indicator and analysis tool of the lexical skill level of not French-speaking learners. By using basic researches in the field of teaching/ learning of the French lexicon, we analyze basic concepts of the lexical field, like lexicon, vocabulary, word, lexeme, lexical access and lexical error, to finally concentrate us on the last concept. What is a lexical error and how should it be apprehended from the didactic point of view? Which approach or method has to adopt a teacher while correcting a lexical error ? We raise in this way the problem of the typology of errors, relevant in the context of didactics of the lexicon, and the problem of taking into consideration some linguistic and discursive parameters during the analysis and the classification of lexical errors. Our approach to a problem of correction of lexical error consists in adopting the principle of rewriting of the erroneous segment. This method allows to associate the linguistic analysis with the didactic reflexion. To support our assumptions, we worked out our own typology of the lexical errors, illustrating it with examples, found in a corpus of 63 written productions of not French-speaking university students