|South, Central, Western Asia, South East Europe and the Caucasus / Total speakers = approximately 1.5 billion in 15 countries|
Distribution of the Indo-Iranian languages
The Indo-Iranian languages (also Indo-Iranic languages or Aryan languages) constitute the largest and southeasternmost extant branch of the Indo-European language family (with over 400 languages), predominantly spoken in the geographical subregion of Southern Asia. They have more than 1.5 billion speakers, stretching from Europe (Romani), Mesopotamia (Kurdish languages, Zaza–Gorani and Kurmanji#Dialect continuum) and the Caucasus (Ossetian, Tat and Talysh) eastward to Xinjiang (Sarikoli) and Assam (Assamese), and south to Sri Lanka (Sinhala) and the Maldives (Maldivian), with branches stretching as far out as Oceania and the Caribbean for Fiji Hindi and Caribbean Hindustani respectively. Furthermore, there are large diaspora communities of Indo-Iranian speakers in northwestern Europe (the United Kingdom), North America (United States, Canada), Australia, South Africa, and the Persian Gulf Region (United Arab Emirates, Saudi Arabia).
The common ancestor of all of the languages in this family is called Proto-Indo-Iranian—also known as Common Aryan—which was spoken in approximately the late 3rd millennium BC. The three branches of the modern Indo-Iranian languages are Indo-Aryan, Iranian, and Nuristani. A fourth independent branch, Dardic, was previously posited, but recent scholarship in general places Dardic languages as archaic members of the Indo-Aryan branch.
The Indo-Iranian languages consist of three groups: 
Indo-Iranian languages are spoken by more than 1.5 billion people.
The languages with the most speakers are a part of the Indo-Aryan group:
Among the Iranian branch, major languages are
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Base on ethnologue have 448 Indo-Iranian languages. Base on glottolog have 583 Indo-Iranian languages.
The common proto-language of the Indo-Iranian languages is the Proto-Indo-Iranian language, which has been reconstructed.
The oldest well-attested Indo-Iranian languages are Vedic Sanskrit, Older and Younger Avestan and Old Persian (ancient Iranian languages). A few words from another Indo-Aryan language (see Indo-Aryan superstrate in Mitanni) are attested in documents from the ancient Mitanni and Hittite kingdoms in the Near East.
Within the Indo-European family, Indo-Iranian belongs to the Satem group. Various proposals have been made that link the Indo-Iranian languages with other subgroups of Indo-European (like Graeco-Aryan, which posits a close relationship with Greek and Armenian), but these remain without wider acceptance.
Innovations shared with other languages affected by the satem sound changes include:
Innovations shared with Greek include:
Innovations unique to Indo-Iranian include:
'Dardic' is a geographic cover term for those Northwest Indo-Aryan languages which [..] developed new characteristics different from the IA languages of the Indo-Gangetic plain. Although the Dardic and Nuristani (previously 'Kafiri') languages were formerly grouped together, Morgenstierne (1965) has established that the Dardic languages are Indo-Aryan, and that the Nuristani languages constitute a separate subgroup of Indo-Iranian.