ISBN : 978-2-7574-1142-1International audienceIt is well known that Old French had developed a system of preverbs expressing aspectual distinctions. In our paper, we concentrate on two homonymic preverbs: (i) a preverb en-which originates from the Latin preposition in and (ii) a preverb en-originating from the anaphoric adverb inde. The analysis of a set of dictionaries and a diachronic corpus reveals that these two preverbs are on the decline in medieval French. This can be explained by the fact that the en-preverbs do not allow the construction of a transparent aspectual system, because the prefixed verbs and the verbal bases are polysemous and because this polysemy gives rise to variable aspectual interpretations. However, the decline of...