Sanskrit isn’t a dead language in the sense of its no longer being a mother tongue. On the contrary, Sanskrit probably has not been a mother tongue for over 2,000 years. Yet it flowered in the first millennium CE into the language of power par excellence for much of South and Southeast Asia. It’s more helpful to think of Sanskrit as a learned language. It is still learned intensively by a range of students in South Asia and one can hear it spoken, for example, in Sanskrit universities in India and Nepal. For a number of years the vitality of the language as a creative medium has been a topic of controversy—and some eminent scholars do consider it a ‘dead language,’ or very nearly so, in that sense.
Sanskrit linguists documented and analyzed the language’s phonology with unparalleled sophistication from a very early date. We have a better understanding of its pronunciation than we do for any other language of premodernity. Also from a very early date dialectal differences are evident in Sanskrit texts, as is the case in modern spoken Sanskrit (though much fewer, for example, than in present-day English). These can be ignored by the beginning student.