Middle Persian (MPers.) and Parthian (Parth.) constitute the western branch of the known Middle Iranian languages. * The term 'Pahlavi' (pahl.) refers to the Middle Persian of the Zoroastrian texts, but is also sometimes used for Middle Persian in general . The indigenous words for the languages may have been Parsig and Pahlawanag 'Parthian' (found in a Manichean text). This usage was sometimes adopted by Western scholars, as well (Herzfeld, Nyberg: Parsik, Pahlavik). Still earlier, Pahlavi and Chaldeo-Pahlavi were used.
The two languages are closely similar in structure, though Parthian shares some features with its eastern neighbors, notably with Bactrian, rather than with Middle Persian. The fact that Manichean Middle Persian and Parthian were two separate languages with different linguistic affinities was first shown by Tedesco. Parthian was spoken in Parthia, east of the Caspian Sea, and became an official language under the Parthian (Arsacid) rulers of Iran (ca. 247 BCE-224 CE). It is known mainly from a large corpus of short, formulaic, Parthian inscriptions mostly on potsherds from the Parthian capital of Nisa dating from the first century BCE; a few royal Parthian inscriptions from the last couple of centuries of Parthian rule; Parthian versions of the inscriptions of the third-century Sasanian kings Ardashir I, Shapur 1, and Narseh; and from the Manichean (Man.) texts found at Turfan in north-eastern Chinese Turkestan (Xinjiang) in the early nineteenth century. On the language of the mostly Aramaic inscriptions from north-western Iran and the Awroman document. Middle Persian is descended from Old Persian (OPers.) and is the ancestor of New Persian (NPers.).
Its proper homeland was the area of Pars in south-western Iran (Gk. Persis), and it was the official language of the local Perside kings (ca. 200 BCE-224 CE) and their successors, the Sasanians (224-651 CE). After the fall of the Sasanians, it continued to be used by the Zoroastrians long after the spoken language had become New Persian in the centuries following the Arab conquest (ca. 650). Middle Persian is known mainly from inscriptions, documents on parchment and papyrus, a translation of the Psalms of David (the 'Pahlavi Psalter' [Ps.]) found at Turfan, the Zoroastrian scriptures, and the Manichean texts from Turfan. A page from a Pahlavi text containing verb forms was also found there.
The earliest inscriptions are those on the coins of the Perside rulers and on a silver bowl from the second half of the first century BCE. There are royal and private inscriptions by high officials and travelers, most of them from the third century, a few from the fourth-fifth centuries; the earliest ones were bilingual (trilingual) Middle Persian, Parthian, (Greek). There are inscriptions on objects (silver bowls, seals, etc.) from the entire Sasanian period. The Zoroastrian and Christian funerary inscriptions are from the late Sasanian and early Muslim period; some are from as far away as India (that on the Thomas Cross from the seventh century, and Xi'an, China. The papyri are probably from the sixth-seventh centuries. A large corpus of mostly legal documents on parchment from the seventh century has recently surfaced and is currently being deciphered and studied.
The earliest Manichean texts may have been composed in the mid-third century, but the manuscripts are much later, and texts were still composed in Turfan in the eighth century. The Psalter manuscript probably dates from the seventh century, although the text is probably older