Old Uighur

the language of the ancient Uighurs, represented by various dialects and similar to the language of the Orkhon Turks—the ancient Oghuz.

Records from the fifth to the ninth centuries include inscriptions in the runic Orkhon alphabet adapted for carving in stone (such as the Selenga Stone) and manuscripts in the Old Sogdian vertical alphabet—Manichaean Uighur manuscripts (such as The Penitential Prayer of the Manichaeans) and, in a lesser number, Buddhist Uighur manuscripts. Records from the tenth to the 15th centuries are Muslim Uighur, written in the Arabic alphabet.