In our household, how does a child learn his/her mother tongue. Let's assume the mother tongue is Hindi. One can observe the child doesn't need to learn the basic alphabet a, aa, e , ee , etc. first . The child learns to speak Hindi even when s/he has no clue what the alphabets look like. The kid first learns to speak the language, then learns the (alphabet) read and write.

However, when we teach kids another language, for example English, they are first made to learn the alphabets, then words, grammar, short-sentence and later speaking.

So, interestingly...

Child learns Hindi by first speaking and then reading and writing but learns English by first reading and writing and then speaking.

To give more context, how do you think a dog (or any pet animal) understands your language ? And here, which language just doesn't matter (fascinating..isn't it?). One might argue that dog understands the expressions more than the language. That's very true. But that's the case with a child also. S/he doesn't understand the words, but the expressions first. It's just that we, humans take it to the next level of writing and reading.

Truth is kids have the innate ability to acquire a language unlike older adults. They do so when they start speaking their mother tongue while imitating adults and learning from activities. But when it comes to other language, we try to feed them with lot of info; they are suffocated with lot of alphabets, grammar rules etc. and in this process they lose the love for the language. Kids are made to feel that it is tough to learn another language which in reality is not true at least for younger ones.

One just needs to give the kid(s) right environment where people are talking in another language; they will pick the language with much ease on their own (without knowing any of alphabet / grammar).