Learn Hardcore Malay: Adat tempatan itu saya tulis dalam diari supaya saya tidak lupa. - I write down those local customs in my diary so that I do not forget.

But Malay also very often uses “topic–comment” structure: you put the topic (what you’re talking about) first, then you comment on it. That gives you orders that look like OSV in English terms.

So:

Adat tempatan itu saya tulis dalam diari…
literally: Those local customs, I write (them) in my diary…

Here:

Adat tempatan itu = the topic (“those local customs”)
saya tulis dalam diari = the comment about that topic (“I write [them] in the diary”)

Both are grammatically correct:

Saya tulis adat tempatan itu dalam diari… – neutral SVO, focuses on what I do.
Adat tempatan itu saya tulis dalam diari… – highlights those customs; slightly more “draws attention” to the object.

English sometimes does this too:
“Those local customs, I write them down in my diary so I don’t forget.”

What exactly does “itu” do in “adat tempatan itu”, and why is it placed after the noun?

“Itu” is a demonstrative meaning roughly “that / those”.

Placement
In Malay, demonstratives normally go after the noun phrase:
- adat tempatan itu = those local customs
- buku itu = that book
- orang tua itu = that old person / that elder
Putting itu before the noun (itu adat tempatan) is not the normal pattern for “that X”.
With or without “itu”
- adat tempatan = local customs (general, not specific)
- adat tempatan itu = those local customs (more specific, ones we both know about from context)
“itu” vs “ini”
- ini = this/these (near the speaker)
- itu = that/those (farther away, or already mentioned / known)
So:
- adat tempatan ini = these local customs (here / we’ve just been talking about them)
- adat tempatan itu = those local customs (already known, or “over there” conceptually or physically)

Can I say “Saya tulis adat tempatan itu…” instead? Is there any difference in meaning?

Yes, you absolutely can say:

Saya tulis adat tempatan itu dalam diari supaya saya tidak lupa.

This is the neutral, straightforward SVO version:

Subject: saya
Verb: tulis
Object: adat tempatan itu

Meaning-wise, it’s the same. The difference is nuance:

Saya tulis adat tempatan itu…
– Feels like you’re focusing on what you do (I write those customs down).
Adat tempatan itu saya tulis…
– Feels like you’re focusing on the customs themselves (Those customs, I write them down…).
– Slightly more “topic-marking” or “emphatic” on adat tempatan itu.

Both are natural. In everyday speech, the SVO version is very common; the topicalized version is also common, especially when you contrast, emphasize, or continue an earlier topic.

What’s the difference between “tulis” and “menulis”? Could I say “saya menulis dalam diari” here?

Both are from the same root:

tulis = root verb “write”
menulis = meN-
- tulis → “to write / writing (in a more explicit or formal sense)”

In this sentence, you can say:

Adat tempatan itu saya tulis dalam diari…
Adat tempatan itu saya menulis dalam diari… ❌ (sounds wrong with this word order)
Saya menulis adat tempatan itu dalam diari… ✅

Key points:

Bare verb vs meN- form
- Bare verb (tulis) is very common in colloquial Malay, especially after pronouns:
  Saya tulis, dia tulis, kita makan, etc.
- meN- verb (menulis) is more explicit, often used in more formal or careful speech/writing.
In this sentence
Natural options:
- Adat tempatan itu saya tulis dalam diari… (topicalized object, bare verb)
- Saya tulis adat tempatan itu dalam diari… (SVO, bare verb)
- Saya menulis adat tempatan itu dalam diari… (SVO, slightly more formal)
Why “Adat tempatan itu saya menulis…” is odd
With topicalization, Malay tends to keep the bare root form:
- Adat tempatan itu saya tulis setiap hari. ✅
  Menulis there sounds unnatural because of the syntax, not because the form is wrong in general.

Why is it “dalam diari” and not just “di diari”? What’s the difference between “di” and “dalam”?

Both di and dalam can relate to location, but they’re used a bit differently.

di = at / in / on (general location)
dalam = in / inside (more “inside-ness”)

In practice:

Concrete space
- di bilik = in/at the room (location)
- dalam bilik = inside the room (emphasis on being inside)
For things like books, diaries, containers
You can find both, but dalam is very common because you’re putting something inside that thing:
- dalam diari = in the diary (inside its pages)
- dalam buku nota = in the notebook
- dalam beg = in the bag
Is “di diari” wrong?
- di diari is understandable, and you might hear it, but dalam diari sounds more natural because you’re conceptually putting information inside the diary.

So:
“Adat tempatan itu saya tulis dalam diari…” feels idiomatic and good.

What exactly does “supaya” mean here, and how is it different from words like “untuk” or “kerana”?

Supaya expresses purpose with a result in mind, similar to:

“so that”,
“in order that”.

In the sentence:

…supaya saya tidak lupa.
= …so that I don’t forget.

Comparison:

supaya / agar
- supaya and agar are very close; both mean “so that”.
- agar is a bit more formal, often seen in writing:
  - …agar saya tidak lupa.
untuk
- untuk = “for / to (do something)”; it focuses more on purpose/goal itself, not on a resulting state.
- You can say:
  - Saya tulis adat tempatan itu dalam diari untuk mengelakkan lupa.
    = I write those local customs in the diary to avoid forgetting.
    Here untuk must be followed by a noun or a verb phrase, not a full finite clause like “saya tidak lupa”.
kerana / sebab
- kerana / sebab = “because” / “since” (reason, not purpose).
- If you say:
  - Saya tulis adat tempatan itu dalam diari kerana saya tidak mahu lupa.
    = I write those customs in the diary because I don’t want to forget.

So, in this sentence supaya is the best choice because we’re talking about an intended result: I write them so that I don’t forget.

Why is it “supaya saya tidak lupa” and not “supaya saya tidak akan lupa” or “supaya saya jangan lupa”?

All of these involve negation and forgetting, but they’re not interchangeable.

supaya saya tidak lupa
- Literally: so that I do not forget.
- tidak lupa is a simple, neutral “not forget”, generic or future-looking from context.
- Very natural here.
supaya saya tidak akan lupa
- akan marks more explicit futurity: “will not forget”.
- Grammatically okay, but often sounds heavier / more formal than needed in everyday speech.
- You’d usually only add akan if you really want to stress the future or formality.
supaya saya jangan lupa
- jangan is used mainly for imperatives (telling someone “don’t do X”).
- So jangan lupa = “don’t forget!” (command / reminder).
- supaya saya jangan lupa sounds odd, because you’re sort of giving yourself a command inside a purpose clause; it’s not idiomatic in standard Malay.

So the natural choice in a statement like this is:

…supaya saya tidak lupa. ✅

Could I drop the second “saya” and just say “supaya tidak lupa”?

Yes, in informal speech, people often drop repeated pronouns if the subject is clear from context:

Adat tempatan itu saya tulis dalam diari supaya tidak lupa.

This is understandable and commonly heard in conversation. The listener will assume the subject of tidak lupa is still “saya”.

However:

supaya saya tidak lupa is clearer and more standard, especially in writing or when you want to avoid ambiguity.

So:

Spoken / casual:
Adat tempatan itu saya tulis dalam diari supaya tidak lupa. ✅
Standard / clear:
Adat tempatan itu saya tulis dalam diari supaya saya tidak lupa. ✅

Does “Adat tempatan itu saya tulis dalam diari…” sound formal, casual, or literary?

It sounds natural and neutral, with a slight lean toward a more careful or narrative style because of the topicalized word order.

Rough guide:

Very casual speech:
- Saya tulis adat tempatan itu dalam diari, nanti tak lupa.
  (Use of tak, maybe nanti instead of supaya.)
Neutral, everyday but correct:
- Saya tulis adat tempatan itu dalam diari supaya saya tidak lupa.
Topic-emphasizing / narrative style (still natural):
- Adat tempatan itu saya tulis dalam diari supaya saya tidak lupa.

So your sentence is fine in both spoken and written Malay, especially when you want to emphasize the customs as the topic.

Could I say “Saya tuliskan adat tempatan itu dalam diari”? What does the “-kan” do here?

Yes, you can say:

Saya tuliskan adat tempatan itu dalam diari supaya saya tidak lupa.

Here, tuliskan = tulis + -kan.

The suffix -kan often:

Adds a sense of doing the action for some purpose / for someone / to something
- tulis = write
- tuliskan ≈ write (it) down / write (it) for someone / write (it) into something
Can make the verb feel a bit more transitive / “applied”:
- Emphasizes that you are writing the customs into the diary.

In this particular sentence:

Saya tulis adat tempatan itu dalam diari…
Saya tuliskan adat tempatan itu dalam diari…

Both are correct and natural. Tulis is more neutral; tuliskan can subtly emphasize the completion / placement of the writing into the diary, but in many contexts they overlap heavily in meaning.