Kamu tidak usah panik, toh rapat belum dimulai.

Tidak usah means no need to or you don’t have to. In this sentence, Kamu tidak usah panik means You don’t need to panic.

Compared with jangan:

• jangan panik = don’t panic
• tidak usah panik = no need to panic

Both can work in similar situations, but tidak usah often sounds a bit softer and more reassuring. It suggests that panic is unnecessary because the situation is still okay.

Yes. Kamu is the ordinary informal word for you.

It is commonly used:

• with friends
• with people around your age
• in casual conversation
• sometimes by a person in a higher position speaking down to someone younger

It is not the most polite choice in formal situations. In a more formal version, you might hear:

• Anda tidak perlu panik, rapat belum dimulai.

So this sentence sounds conversational and fairly informal.

Toh is a discourse particle. It adds the feeling of after all, anyway, or as it is.

In this sentence:

• Kamu tidak usah panik, toh rapat belum dimulai.

the speaker is saying something like:

• No need to panic, after all the meeting hasn’t started yet.

So toh gives the reason or justification for the first clause. It is very natural in speech, but it can be tricky because it often does not translate neatly word-for-word.

This is a very common learner question.

• belum = not yet
• tidak = not

So:

• rapat belum dimulai = the meeting has not started yet
• rapat tidak dimulai = the meeting was not started / did not start
  This sounds more like the meeting did not happen or was not started at all.

Because the meaning is that the meeting simply hasn’t started yet, belum is the correct choice.

Dimulai is the passive form of memulai.

• memulai = to start something
• dimulai = to be started

So:

• rapat belum dimulai = the meeting has not been started yet

This is very natural Indonesian.

You may also hear:

• rapat belum mulai

That is also common in everyday Indonesian and means basically the same thing.
The version with dimulai can sound a little more complete or standard.

In Indonesian, words are often more flexible than in English. Panik can behave like a stative predicate, and after tidak usah it works naturally as the thing you are being told not to do.

So in:

• tidak usah panik

panik is best understood as to panic / be panicked in context.

English often forces a clearer category distinction than Indonesian does.

Yes, to some extent.

You could say:

• Toh rapat belum dimulai, kamu tidak usah panik.

This puts the reason first: After all, the meeting hasn’t started yet, so you don’t need to panic.

The original order is probably more natural if the speaker first wants to calm the person down, then explain why.

The comma helps separate the two clauses:

• Kamu tidak usah panik
• toh rapat belum dimulai

It reflects a natural pause in speech. It is especially helpful because toh introduces the reason or justification for what was just said.

In casual writing, people may sometimes leave punctuation out, but the comma is good standard writing here.

It sounds natural and fairly casual-conversational.

Why?

• kamu is informal
• toh is common in speech and informal writing
• tidak usah is everyday language

A more formal version might be:

• Anda tidak perlu panik, rapat belum dimulai.

That said, the original sentence is perfectly normal in casual Indonesian.

Yes.

• Kamu tidak usah panik = You don’t need to panic
• Kamu tidak perlu panik = You don’t need to panic

Both are correct. The difference is mostly one of tone:

• tidak usah often sounds more conversational and direct
• tidak perlu can sound a bit more neutral or slightly more formal

So the sentence could also be:

• Kamu tidak perlu panik, toh rapat belum dimulai.

That would still sound natural.