This work is devoted to the morphological and syntactic changes in the Persian verbal system between the 10th and 16th centuries. Ten representative prose texts (from various regions and dialects, including Early Judaeo-Persian) have shown the following evolutions. The new analytical passive uses various auxiliaries before one of them, šudan, "to become", overcomes (12th century). The infinitive and the past participle change jointly: the infinitive in an disappears in favour of the short infinitive (kard) when the old past participle kard is replaced by the karda participle (13th-14th centuries). The Middle-Persian adverb hamē is grammaticalized in prefix mē and its principal value of concomitance has gradually weakened. The suffix ē, marker of the past habitual and the counterfactual, declined in favour of mē (15th century). Gradually the perfect has also been used to express the evidential. The periphrastic future, formed with xvāstan, "to want", at first marks an intention-based future, then also expresses a prediction-based future (14th century). Although the system is unravelling at the 15th century, the prefix bi¬ is a marker of rhematicity throughout the period and the opposition indicative/subjunctive is not yet recreated. buvad, "is", is replaced by bāšad; at the times when they coexist (10th-11th centuries), buvad marks the inherent and bāšad, the transient. As for the construction of modal verbs, it went from a governed infinitive to a governed finite verb, whose morphology is richer (14th-16th centuries). As a result, without crystallizing all the changes, the 15th century is a milestone in the evolution of Persian verbal system.
