---

In Modern Persian, different forms of the verb “goftan” (meaning “to say”) are used as grammatical tools for denoting modality. Some of these forms such as “gu”, “gu’i”, “gofti”, “gu’iyâ” and “guyâ” went through historical changes and were used as modal adverbs in Persian literary texts and among them, “gu’i” and “guyâ” are still common. In Modern Persian, there are other forms of the verb “goftan” such as “begu”, “nagu” and “begu’i”, which function as modals in certain contexts. In this paper, we studied the semantic features of the verb “goftan” in texts belonging to different stages of Persian language from Old Persian to Modern Persian and we also tracked the process of grammaticalization of certain forms of the verb “goftan” to show how they changed into modal adverbs. Based on our findings, “gu’i” has been used for purposes such as simile and allegory to represent imaginary and unreal statements and “guyâ” has had a modal role to represent doubt and uncertainty of the speaker. Both forms are still in use. Moreover, some forms of the verb “goftan” are in the middle stages of grammaticalization. These forms represent the modalities of inference, conjecture, assumption, and imagination, but some of them are gradually losing their verbal characteristics and are changing into adverbs to represent modality.