Indo-Aryan languages

Definition and stakes

George Abraham Grierson 1911 Encyclopædia Britannica (1911)

Relations with other Indo-Aryan Languages.—Marathi has to its north, in order from west to east, Gujarati, Rajasthani, Western Hindi and Eastern Hindi. To its east and south it has the Dravidian languages, Gondi, Telugu and Kanarese. Elsewhere in India Aryan languages gradually fade away into each other, so that it is impossible to fix any definite boundary line between them. But this is not the case with Marathi.
Source: Wikisource

George Abraham Grierson 1911 Encyclopædia Britannica (1911)

As explained in the article Indo-Aryan Languages, there were in ancient times two main groups of these forms of speech—one, the language of the Midland, spoken in the country near the Gangetic Doab, and the other, the languages of the so-called “Outer Band,” containing the Midland on three sides, west, east and south. The country to the south of the Midland, in which members of this Outer group of languages were formerly spoken, included the modern Rajputana and Gujarat, and extended to the basin of the river Nerbudda, being bounded on the south by the Vindhya hills.
Source: Wikisource

Various Encyclopaedia Britannica, 11th Edition…

The whole family occupies the three-sided tract of country between the Hindu-Kush and the north-western frontier of British India.
As explained in Indo-Aryan Languages, the Piśāca languages are Aryan, but are neither Iranian nor Indo-Aryan. They represent the speech of an independent Aryan migration over the Hindu-Kush directly into their present inhospitable seats, where they have developed a phonetic system of their own, while they have retained unchanged forms of extreme antiquity which have long passed out of current use both in Persia and in India.
Source: Gutenberg

Get perspective with Kwize: daily news enlightened by great literature