By what age does a child essentially master their language's sound system and grammar and acquire a vocabulary of thousands of words?

→ Who plays the most important role in learning the English language? → Through what means can a child acquire their mother tongue? → The sensitive period for language development is: → Who gave the theory of language development? → Under which Article of the Indian Constitution is provision made for states to provide adequate facilities for instruction in the mother tongue at the primary stage of education? → First language acquisition does not include the following stage-