Classification
Soon after postulating an Indo-European family in the 19th century, the Iranian languages (Avestan, Old Persian, Pahlavi) together with Indic (Sanskrit, Prakrit) were recognized by works of the linguist Rasmus Rask in 1826 as the eastern branch of Indo-European languages. Due to an enormous amount of (middle) Iranian loanwords the Armenian language initially was also classified as an Iranian language but (in 1875) Hübschmann established it as a separate language branch of the Indo-European language family.
Iranian languages are divided into Eastern and Western subfamilies, totalling about 84 languages (SIL estimate). Of the most widely-spoken Iranian languages, Kurdish, Persian, and Balochi are all Western Iranian languages, while Pashto is an Eastern Iranian language.
Read more about this topic: Iranian Languages