Coba tebak siapa yang mengetuk pintu.

Literally, coba means try. In everyday Indonesian, when it appears before a command, it often softens the tone and makes it sound more natural or encouraging.

So Coba tebak... can mean:

• Try to guess...
• Go ahead, guess...
• Come on, guess...

It is very common in speech.

Tebak is the base form, and in commands Indonesian often uses the base form directly.

So:

• Tebak! = Guess!
• Coba tebak... = Try to guess...

Menebak is the active verb form more commonly used in statements, such as:

• Saya menebak jawabannya = I guessed the answer

After coba, the bare verb tebak sounds very natural.

It is omitted because Indonesian imperatives usually do not mention the subject. The you is understood from context.

So Coba tebak... naturally means:

• You, try to guess...

You could say Kamu coba tebak..., but that is only used when you want extra emphasis or contrast. Most of the time, leaving kamu out sounds more natural.

In standard Indonesian, siapa yang ... is the usual and most natural way to say who ... when who is the subject of the verb.

So:

• siapa yang mengetuk pintu = who knocked / who is knocking on the door

The word yang links siapa to the action that follows. Without yang, the sentence may sound less natural or less standard in many contexts.

Yang is a very common Indonesian linker. It often connects a noun or pronoun to a describing clause.

In this sentence:

• siapa yang mengetuk pintu

you can think of it as meaning something like:

• who is the one that knocked on the door
• who it is that knocked on the door

In natural English, we usually do not translate yang as a separate word, but grammatically it is doing important linking work.

It comes from the root ketuk, which means knock.

Indonesian adds the active prefix meN-:

• ketuk → mengetuk

Because the root begins with k, that k disappears after the prefix is added. This is a common sound change in Indonesian morphology.

So:

• root: ketuk
• active verb: mengetuk

Indonesian often expresses this idea without a separate preposition.

So:

• mengetuk pintu literally looks like knock door
• but it naturally means knock on the door

This is just how the verb is commonly used. English needs on, but Indonesian usually does not here.

Indonesian verbs do not change form for tense the way English verbs do.

So mengetuk by itself does not tell you whether the action is:

• knocked
• is knocking
• has knocked

The time is understood from context.

In this sentence, English could translate it in different ways depending on the situation:

• Try to guess who knocked on the door
• Try to guess who is knocking on the door

Both are possible.

Indonesian does not have articles like a, an, and the.

So pintu can mean:

• a door
• the door

Context tells you which one is meant. In this sentence, it is naturally understood as the door.

No. The whole sentence is actually a command or prompt:

• Coba tebak = Try to guess

The part siapa yang mengetuk pintu is an embedded question inside that command.

That is why the sentence can be written with a period:

• Coba tebak siapa yang mengetuk pintu.

In English, the same thing happens:

• Try to guess who knocked on the door.

Yes. That is also correct.

The difference is tone:

• Coba tebak... = softer, more conversational
• Tebak... = more direct

Both are natural, but coba makes it sound a little friendlier or less abrupt.