Sanskrit is traceable to the 2nd millennium BCE in a form known as Vedic Sanskrit with the Rigveda as the earliest-known composition. The standardized Classical and Epic Sanskrit was a literary language and not the ancestor of any Indo-Aryan language Sanskrit has significantly influenced the grammar, phonology and vocabulary of the Tamil, Kannada, Telugu and Malayalam languages of South India

A more refined and standardized grammatical form called Classical Sanskrit emerged in the mid-1st millennium BCE, the broader definition of Sanskrit refers to the whole range of mutually intelligible Old Indo-Aryan dialects spoken in North-western India at the time of the composition of the Vedas and thus can be treated as the ancestor of the Prakrits and Pali, and consequently, of all Modern Indo Aryan languages like Hindi, Marathi, Bengali, Punjabi, Gujrathi, Sindhi, Kashmiri, Kumaoni, Garhwali, Urdu, Dogri, Konkani, Marathi, Assamese, Odia and Nepali.

Colonial era scholars familiar with Latin and Greek were struck by the resemblance of the Sanskrit language, both in its vocabulary and grammar, to the classical languages of Europe.[note 4] It suggested a common root and historical links between some of the major distant ancient languages of the world.

In order to explain the common features shared by Sanskrit and other Indo-European languages, the Indo-Aryan migration theory states that the original speakers of what became Sanskrit arrived in the Indian subcontinent from the north-west sometime during the early second millennium BCE. Evidence for such a theory includes the close relationship between the Indo-Iranian tongues and the Baltic and Slavic languages, vocabulary exchange with the non-Indo-European Uralic languages, and the nature of the attested Indo-European words for flora and fauna.[63] The pre-history of Indo-Aryan languages which preceded Vedic Sanskrit is unclear and various hypotheses place it over a fairly wide limit.