[6] The Middle-Iranian ērān and aryān are oblique plural forms of gentilic nouns ēr- (Middle Persian) and ary- (Parthian), both deriving from Proto-Iranian language *arya- (meaning "Aryan", i.e. "of the Iranians"),[6][7] recognized as a derivative of Proto-Indo-European language *ar-yo-, meaning "one who assembles (skilfully)".

[8] In the Iranic languages spoken on the plateau, the gentilic is attested as a self-identifier, included in ancient inscriptions and the literature of the Avesta,[9][note 1] and remains also in other Iranian ethnic names Alan (Ossetian: Ир Ir) and Iron (Ирон).

[citation needed] The language was situated precisely in the western part of Central Asia that borders present-day Russia and Kazakhstan.

Old Persian was an Old Iranian dialect as it was spoken in southwestern Iran (the modern-day province of Fars) by the inhabitants of Parsa, Persia, or Persis who also gave their name to their region and language.

Later inscriptions are comparatively brief, and typically simply copies of words and phrases from earlier ones, often with grammatical errors, which suggests that by the 4th century BCE the transition from Old Persian to Middle Persian was already far advanced, but efforts were still being made to retain an "old" quality for official proclamations.

[22] These terms have little meaning with respect to Old Avestan as that stage of the language may predate the settling of the Iranian peoples into western and eastern groups.

These concern the fate of the Proto-Indo-Iranian first-series palatal consonants, *ć and *dź:[23] As a common intermediate stage, it is possible to reconstruct depalatalized affricates: *c, *dz.

Linguistically the Middle Iranian languages are conventionally classified into two main groups, Western and Eastern.

The Western family includes Parthian (Arsacid Pahlavi) and Middle Persian, while Bactrian, Sogdian, Khwarezmian, Saka, and Old Ossetic (Scytho-Sarmatian) fall under the Eastern category.

[24] The Achomi (Larestani/Khodmooni) language is considered a surviving remains of Pahlavi Middle Persian,[25][26][27][28][29][30][31] as well as Luri, with their respective dialects.

Following the Arab conquest of Persia, there were important changes in the role of the different dialects within the Persian Empire.

The old prestige form of Middle Iranian, also known as Pahlavi, was replaced by a new standard dialect called Dari as the official language of the court.

The name Dari comes from the word darbâr (دربار), which refers to the royal court, where many of the poets, protagonists and patrons of the literature flourished.

Medieval Iranian scholars such as Abdullah ibn al-Muqaffa (8th century) and Ibn al-Nadim (10th century) associated the term "Dari" with the eastern province of Khorasan, while they used the term "Pahlavi" to describe the dialects of the northwestern areas between Isfahan and Azerbaijan, and "Pârsi" ("Persian" proper) to describe the dialects of Fars (Persia).

The Islamic conquest also brought with it the adoption of the Arabic script for writing Persian and much later, Kurdish, Pashto and Balochi.

In Eastern Europe, mostly comprising the territory of modern-day Ukraine, southern European Russia, and parts of the Balkans, the core region of the native Scythians, Sarmatians, and Alans had been decisively taken over as a result of absorption and assimilation (e.g. Slavicisation) by the various Proto-Slavic population of the region, by the 6th century CE.

Sogdian's close relative Yaghnobi barely survives in a small area of the Zarafshan valley east of Samarkand, and Saka as Ossetic in the Caucasus, which is the sole remnant of the once predominant Scythian languages in Eastern Europe proper and large parts of the North Caucasus.