[9][10][11][12] The main dynamics of the linguistic evolution of modern Persian are political and social changes such as population shifts, the advancement of particular regions, and the rise of ideological influences.

It is likely that the multiple relocations of the capital city of Iran itself influenced the development of a distinctive metropolitan sociolect that would affect Persian dialects throughout the country.

[4] During the late 12th and late 15th or early 17th centuries in Iran, the vowel repertory of the Persian language was reduced and a few consonants were altered in most of Iran's Western Persian dialects, while these features have been predominantly preserved in the Eastern dialects of Dari and Tajik up until the present day.

[4] From the time of the Turco-Mongol invasions to the Safavid and subsequent Turkic-speaking dynasties, Persian received a number of lexical borrowings from Turkish, although never as much as those from Arabic.

[15] The dialects of Dari spoken in Northern, Central and Eastern Afghanistan, for example in Kabul, Mazar, and Badakhshan, have distinct features compared to Iran's Standard Persian.