"You can use both of them in a formal/informal situation. But, personally, the word "Aku" has a cute/soft tone. Hehe!.

"The word "Kamu" means you as singular, while "Kalian" means you as plural. So, whenever you have a speech in front of a group of people, you'd better use "kalian". Sometimes, I replace the word "kalian" by using a phrase "Kamu semua", and it has a neutral tone."

Example:

- Kamu istriku satu-satunya = You're my only love.

- Kalian adalah murid kesayanganku = You guys are my beloved student!

- Kamu semua adalah murid kesayanganku = You guys are my beloved student!

"The differences between those words are the one is exclusive (Kami) and the other is inclusive (Kita)."

Example:

- Kami tidak suka itu! = We don't like it! <em>(let say, my wife and I are talking to our kids)</em>

- Kita harus lebih baik lagi! = We have to make it better next time! <em>(let say, you're a boss and encouraging your team)</em>

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That's for today! If you have any questions, feel free to ask me.

<em>Salam</em>,

Dindin