Abstract : Cross-linguistically, indefinite articles tend to emerge later than definite articles. The grammaticalization process that will lead to the indefinite articles un and du/ des of Modern French is still in a very early stage in Old French. Uns is indeed still close to its source meaning, the numeral value, both in its quantitative dimension of uniqueness marker (‘only one’) and in its qualitative dimension of identity marker (‘one and the same’). It has nevertheless acquired a textual role in Old French, which attests its shift towards the status of article: on the one hand, in line with the quantitative numeral meaning, it delimits an entity and introduces it as a new prominent discourse referent; on the other hand, according to its qualitative numeral meaning, it introduces a new type or a new category. As to the partitive, it is claimed that it has not reached the status of article in Old French, but has an intermediate status, between preposition and determiner. This hypothesis offers an account for the low frequency of the partitive, for its hybrid syntactic properties and for its specific meaning of indefinite extraction from a concrete and contextually definite partition set. From a methodological viewpoint, this study illustrates that a synchronic analysis gains by being combined with a diachronic perspective: a more comprehensive account of the exact meaning and the specific conditions of uses of uns and of the partitive in Old French can be offered if the analysis is based upon a correct definition of the source expression, evaluates its evolutionary stage with respect to this source and fits into an overall picture of the grammaticalization path towards the status to full-fledged article.