“Indo-Aryan: Branch, within Indo-European, of Indo-Iranian: first attested by texts in Vedic (Sanskrit) dating from the 2nd millenium BC, and by transcriptions from the first. Also called ‘Indic.’
The modern Indo-Aryan languages are indigenous to most of the north and centre of the Indian subcontinent, with outliers in Sri Lanka (Ceylon) and the Maldives. Hindi-Urdu and Bengali are by far the largest; of the remainder, Marathi, in the south of the main area, Gujarati in the south-west, Sindhi to the west, Punjabi in the north-west, Assamese in the east, Oriya in the south-east, and Sinhalese in Sri Lanka all have a current literary standard and are linked to major political units. Others, such as Bhojpuri or Maithili, also have speakers in the tens of millions.
Across the main area, separate languages have arisen largely by divisions within a geographical continuum. Hence internal branches are not definitively established.”
Excerpted from: Marshall, P.H., ed. The Oxford Concise Dictionary of Linguistics. New York: Oxford University Press, 2014.