Learn Hardcore Indonesian: Sejak mula, kami sudah tahu tujuan rapat ini. - From the beginning, we already knew the purpose of this meeting.

sejak awal = since the beginning (very common, neutral)
dari awal = from the beginning (also very common)
sejak mula = since the beginning, but sounds a bit more formal, literary, or old‑fashioned

So you could very naturally say:

Sejak awal, kami sudah tahu tujuan rapat ini.
Dari awal, kami sudah tahu tujuan rapat ini.

Both are more typical in everyday speech than Sejak mula, but the meaning is the same.

Why do we need sudah in kami sudah tahu? Could we just say kami tahu?

Sudah marks that something is already true or has already happened.

kami tahu tujuan rapat ini = we know the purpose of this meeting (a general fact, without the idea of “already”)
kami sudah tahu tujuan rapat ini = we already knew / had already known the purpose of this meeting

In your sentence, Sejak mula, kami sudah tahu tujuan rapat ini, sudah fits well because:

sejak (since) + sudah (already) together emphasise that even from the very beginning, this was already known.

If you drop sudah, the sentence is still grammatically correct, but you lose that “already” nuance.

Can I use telah instead of sudah here? Is there any difference between sudah and telah?

Yes, you can say:

Sejak mula, kami telah tahu tujuan rapat ini.

Telah and sudah both mean already, but:

sudah is more common in everyday conversation and neutral writing.
telah sounds more formal, bookish, or official (often found in news, reports, official letters).

So:

For speech and casual writing: sudah is more natural.
For formal documents or very formal style: telah is fine or even preferred.

The meaning in this sentence doesn’t really change; only the level of formality does.

What is the difference between kami and kita? Could I say Sejak mula, kita sudah tahu tujuan rapat ini?

Both kami and kita mean we, but they differ in inclusiveness:

kami = we (NOT including the person you’re talking to) – exclusive
kita = we (INCLUDING the person you’re talking to) – inclusive

So:

Sejak mula, kami sudah tahu tujuan rapat ini.
= Since the beginning, we (but not you) already knew the purpose of this meeting.
Sejak mula, kita sudah tahu tujuan rapat ini.
= Since the beginning, we (you and I / all of us here) already knew the purpose of this meeting.

Both are grammatically correct; you choose based on who is included in we.

What exactly does tujuan mean here? Is it more like “purpose”, “goal”, or “agenda”?

Tujuan literally means goal, aim, or purpose.

In the context of a meeting:

tujuan rapat ini = the purpose/aim of this meeting
(Why is this meeting being held? What is it trying to achieve?)

This is slightly different from agenda:

agenda rapat ini = the agenda of this meeting (the list of topics / schedule)

So:

tujuan = the overall reason or objective
agenda = the specific items to be discussed

If you want to talk about “agenda” in the strict sense, use agenda, not tujuan.

What does rapat mean, and how is it different from other words like pertemuan?

Rapat means meeting, usually:

more formal
often work‑related, organizational, or official (e.g. office meeting, committee meeting)

Pertemuan is also “meeting” but wider in meaning:

can be any kind of meeting or encounter
can be formal or informal, even a friendly get‑together

Examples:

rapat kerja = work meeting
rapat komite = committee meeting
pertemuan keluarga = family gathering
pertemuan pertama kami = our first meeting (as in “the first time we met”)

So tujuan rapat ini strongly suggests a formal or semi‑formal meeting, not just a casual hangout.

Why is there a comma after Sejak mula? Is it required?

The comma is used because Sejak mula is an introductory time phrase (Since the beginning).

Indonesian punctuation is somewhat flexible, but:

When a time/adverb phrase comes first, a comma is common and recommended, especially in writing:
- Sejak mula, kami sudah tahu tujuan rapat ini.
- Besok, saya akan berangkat.

You could technically write it without a comma in informal contexts:

Sejak mula kami sudah tahu tujuan rapat ini.

It’s still understandable and used in informal writing, but the version with a comma is clearer and more standard.

How does Indonesian express tense in this sentence? Does it mean “knew”, “have known”, or “know”?

Indonesian does not mark tense by changing the verb form. Verbs stay the same.

The sense of time comes from:

Time words: sejak (since), kemarin (yesterday), etc.
Aspect words: sudah (already), sedang (in progress), akan (will), etc.

In Sejak mula, kami sudah tahu tujuan rapat ini:

sejak
- mula = since the beginning
sudah = already

So in natural English, this could be:

“We already knew the purpose of this meeting from the beginning.”
“We’ve known the purpose of this meeting from the start.”

There is no strict past vs present form in Indonesian; the context gives you the time frame.

Could I move sejak mula to the end and say Kami sudah tahu tujuan rapat ini sejak mula?

Yes, that is grammatically correct:

Kami sudah tahu tujuan rapat ini sejak mula.

Both orders are possible:

Sejak mula, kami sudah tahu tujuan rapat ini.
Kami sudah tahu tujuan rapat ini sejak mula.

The difference is only in emphasis:

At the beginning: Sejak mula is highlighted (focusing on the time).
At the end: the focus is more on kami sudah tahu tujuan rapat ini, and sejak mula just adds extra information.

In everyday speech, both word orders sound natural.

What is the difference between mula and mulai? They look similar.

They are related, but used differently:

mulai is a verb: to begin / to start
- Rapat mulai jam dua. = The meeting starts at two.
- Kita mulai sekarang. = We start now.
mula is more like a noun or part of fixed expressions meaning “beginning”:
- sejak mula = since the beginning
- dari mula sampai akhir = from beginning to end

In modern everyday Indonesian, mula is not very productive; you mostly see it in set phrases like sejak mula. The more common everyday word in other contexts is mulai.

Is there any difference in nuance between Sejak mula, kami sudah tahu tujuan rapat ini and Dari awal, kami sudah tahu tujuan rapat ini?

The basic meaning is the same: from/since the beginning, we already knew the purpose of this meeting.

Nuances:

Sejak mula
- sounds a bit more formal, literary, or old‑fashioned
- less common in casual speech
Dari awal
- very common and natural in everyday conversation
- neutral in tone

In most modern, casual contexts, Dari awal, kami sudah tahu tujuan rapat ini would probably be the first choice, but Sejak mula is still correct and understandable.

What is the overall register of this sentence? Is it formal, casual, or something in between?

The sentence is mostly neutral‑formal:

Words like kami, tujuan, rapat are neutral and perfectly fine in both spoken and written Indonesian.
The phrase Sejak mula pushes it slightly toward a more formal or literary feel.

You could hear this in:

work or organizational contexts
semi‑formal discussions
written texts (emails, reports, etc.)

In very casual speech, a speaker might instead say something like:

Dari awal, kita udah tahu tujuan rapat ini.

Here kita and udah (colloquial sudah) make it more informal.