Avestan /əˈvɛstən/, formerly also known as "Zend", is an Iranian language of the Eastern Iranian division, known only from its use as the language of Zoroastrian scripture, i.e. the Avesta, from which it derives its name. Its area of composition comprised ancient Arachosia, Aria, Bactria, and Margiana, corresponding to the entirety of present-day Afghanistan, and parts of Pakistan, Tajikistan, Turkmenistan, and Uzbekistan. The Yaz culture of Bactria-Margiana has been regarded as a likely archaeological reflection of the early Eastern Iranian culture described in the Avesta.
Avestan's status as a sacred language has ensured its continuing use for new compositions long after the language had ceased to be a living language. It is closely related to Vedic Sanskrit, the oldest preserved Indo-Aryan language.
"Avestan, which is associated with northeastern Iran, and Old Persian, which belongs to the southwest, together constitute what is called Old Iranian." The Old Iranian language group is a branch of the Indo-Iranian language group. Iranian languages are traditionally classified as "eastern" or "western", and within this framework Avestan is classified as eastern. But this distinction is of limited meaning for Avestan, as the linguistic developments that later distinguish Eastern from Western Iranian had not yet occurred. Avestan does not display some typical (South-)Western Iranian innovations already visible in Old Persian, and so in this sense, "eastern" only means "non-western". That is not to say that Avestan does not display any characteristic innovations of its own – e.g., the sibilant pronunciation of the consonant in aša, corresponding to original /rt/ that is preserved in the Old Persian form (arta), as well as Sanskrit (rta).
The Avestan alphabet is a writing system developed during Iran's Sassanid era (226 CE–651) to render the Avestan language.
As a side effect of its development, the script was also used for Pazend, a method of writing Middle Persian that was used primarily for the Zend commentaries on the texts of the Avesta. In the texts of Zoroastrian tradition, the alphabet is referred to as din dabireh or din dabiri, Middle Persian for "the religion's script".
The development of the Avestan alphabet was initiated by the need correctly to represent recited Avestan language texts. The various text collections that today constitute the canon of Zoroastrian scripture are the result of a collation that occurred in the 4th century, probably during the reign of Shapur II (309–379). It is likely that the Avestan alphabet was an ad hoc innovation related to this – "Sassanid archetype" – collation.
The enterprise, "which is indicative of a Mazdean revival and of the establishment of a strict orthodoxy closely connected with the political power, was probably caused by the desire to compete more effectively with Buddhists, Christians, and Manicheans, whose faith was based on a revealed book". In contrast, the Zoroastrian priesthood had for centuries been accustomed to memorizing scripture — following by rote the words of a teacher-priest until they had memorized the words, cadence, inflection and intonation of the prayers. This they passed on to their pupils in turn, so preserving for many generations the correct way to recite scripture. This was necessary because the priesthood considered (and continue to consider) precise and correct enunciation and cadence a prerequisite of effective prayer. Further, the recitation of the liturgy was (and is) accompanied by ritual activity that leaves no room to attend to a written text.
Avestan is a Unicode block containing characters devised for recording the Zoroastrian religious texts, Avesta, and was used to write the Middle Persian, or Pazand language.