Dokter menjelaskan operasi besok.

The basic order is:

Subject + Verb + Object + Time expression

So here:

• Dokter = subject
• menjelaskan = verb
• operasi = object
• besok = time expression

This is a very common Indonesian sentence pattern. Indonesian word order is often similar to English in simple statements.

Indonesian does not use articles like a, an, or the.

So:

• dokter can mean a doctor or the doctor
• operasi can mean an operation, the operation, or surgery, depending on context

Context usually tells you which one is meant. If you want to be more specific, Indonesian can add other words, for example:

• seorang dokter = a doctor
• dokter itu = the doctor
• operasi itu = the operation

Menjelaskan means to explain.

It comes from jelas, which means clear. With the affixes meN- and -kan, it becomes a verb meaning roughly to make clear or to explain.

So:

• jelas = clear
• menjelaskan = explain / make clear

This is a very common Indonesian verb.

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

So menjelaskan can be understood as:

• explains
• explained
• will explain

The time is usually understood from context or from time words like:

• besok = tomorrow
• kemarin = yesterday
• sekarang = now

Because this sentence has besok, English will usually translate it with a future meaning, such as will explain.

Here, operasi is a noun and it is the object of menjelaskan.

It usually means:

• operation
• surgery

depending on context.

So in this sentence, the doctor is explaining the operation / the surgery.

In Indonesian, menjelaskan normally takes a direct object.

So:

• menjelaskan operasi = explain the operation

This is normal and natural.

You may also hear menjelaskan tentang operasi, but many learners are taught that this is less direct and can sound redundant, because menjelaskan already contains the idea of explaining something. Standard textbook Indonesian usually prefers:

• menjelaskan operasi

rather than

• menjelaskan tentang operasi

This is a very good question, because the sentence can be ambiguous.

Besok at the end can often be understood as modifying the whole clause:

• The doctor will explain the operation tomorrow

But it can also be understood as part of the noun phrase:

• The doctor explained tomorrow’s operation
• The doctor explained the operation scheduled for tomorrow

In real life, context usually makes the meaning clear.

If you want to avoid ambiguity, Indonesian can be more explicit. For example:

• Besok dokter akan menjelaskan operasi itu. = Tomorrow the doctor will explain the operation.
• Dokter menjelaskan operasi yang akan dilakukan besok. = The doctor explained the operation that will be done tomorrow.

Yes.

By itself, dokter does not tell you whether it is definite or indefinite. It can mean:

• a doctor
• the doctor
• sometimes even doctors in the right context

If you want to make it clearer, you can say:

• seorang dokter = a doctor
• dokter itu = the doctor

So the original sentence leaves that open unless the wider context already identifies the doctor.

You can add the listener with kepada or pada.

For example:

• Dokter menjelaskan operasi itu kepada pasien. = The doctor explains the operation to the patient.
• Dokter akan menjelaskan operasi itu kepada keluarga pasien besok. = The doctor will explain the operation to the patient’s family tomorrow.

So the pattern is often:

Subject + menjelaskan + thing explained + kepada/pada + person

It is grammatical and understandable, but in real conversation many speakers would make it a little clearer.

For example, if the meaning is that the explanation happens tomorrow, people often say:

• Dokter akan menjelaskan operasi besok.

Adding akan makes the future meaning more explicit.

If the meaning is that the operation itself is tomorrow, people might say:

• Dokter menjelaskan operasi yang dijadwalkan besok.
• Dokter menjelaskan operasi untuk besok.

So the original sentence is possible, but it depends heavily on context.

Yes. Indonesian time expressions are fairly flexible.

All of these can work, depending on emphasis and context:

• Dokter menjelaskan operasi besok.
• Besok dokter menjelaskan operasi.
• Dokter besok menjelaskan operasi.
  This last one is less common and can sound awkward unless the context supports it.

A very common and clear option is:

• Besok, dokter akan menjelaskan operasi.

Putting besok at the beginning often makes it clearer that tomorrow refers to the whole event.