Persian language, member of the Iranian group of the Indo-Iranian subfamily of the Indo-European family of languages (see Indo-Iranian languages). The official language of Iran, it has about 38 million speakers in Iran and another 8 million in Afghanistan. Historically the Persian language falls into three periods: Old, Middle, and Modern. Old Persian is known chiefly from cuneiform inscriptions dating from the time of the Achaemenid kings of ancient Persia (6th–4th cent. BC). Old Persian was highly inflected, as was Avestan, which is regarded by some as a form of Old Persian and by others as a separate tongue. Avestan was the language of the sacred texts of Zoroastrianism that are known as the Avesta (probably composed c.7th–5th cent. BC). Middle Persian derives directly from Old Persian. Also called Pahlavi, Middle Persian prevailed under the Sassanid, or Sassanian, rulers of Persia (3d–7th cent. AD). Grammatically, much simplification of inflection took place in Middle Persian, which was recorded both in an Aramaic alphabet and in a script called Pahlavi. Middle Persian also had a noteworthy literature of Manichaean and Zoroastrian texts. The modern form of Persian evolved directly from Middle Persian and may be said to have begun in the 9th or 10th cent. AD It has not changed much since that date. The grammar of Modern Persian is comparatively simple. The inflection of nouns and verbs has been greatly reduced since the ancient stage of the language. A number of Arabic words were added to the vocabulary as the result of the conquest of the Persians by the Muslim Arabs in the 7th cent. AD Modern Persian is the medium of an old and great literature and is written in a modification of the Arabic alphabet. Modern Persian is also known as Fārsī.

See R. G. Kent, Old Persian (1950); A. K. S. Lambton, Persian Grammar (1971).