Pourquoi nessun / nessuno en italien mais *auque / aucun en français?

The aim of the paper is to analyse the phenomenon of the allomorphism of the Italian indefinite pronoun nessun and its lack in its French equivalent aucun. Whereas the former appears in the variant forms nessun / nessuno, the latter remains unchanged irrespective of the syntactic function it performs. Having analysed the phonological hypothesis, the author attempts to demonstrate that the alternation is not exclusively limited to phonological conditions, but is also caused by syntactic aspects: the autonomy of the full form and the dependence of the shorter form. It is also hypothesised here that the lack of the form *auque in contemporary French stems from the very nature of the negation process of which the form aucun is an exponent.