Answer:
Sanskrit is the language from which most modern languages of the Indian subcontinent evolved, somewhat like how many Western European languages evolved from Latin.
Sanskrit is one of the classical languages of India and the language in which many of Hindu scriptures are written. It is a derivative of the PIE (Proto-Indo-European) language just as many languages around the world are. The Hindu scripture Vedas use an older form of Sanskrit which is known as Vedic Sanskrit. Around 4th to 6th Century BC, a great grammarian Panini codified Sanskrit. Since then, that has become the Standard Sanskrit. Apart of religious literature, Sanskrit also has wonderful secular literature (epics, poetry and drama). For these reasons, Sanskrit is important to hindus.
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