Learn Hardcore Indonesian: Kadang-kadang saya menulis fantasi singkat di buku harian sebelum tidur. - Sometimes I write a short fantasy in my diary before sleeping.

Kadang-kadang = the standard, neutral way to say sometimes.
Kadang on its own is also used in everyday speech and is a bit shorter and more casual, but the meaning is the same.

Examples:

Kadang-kadang saya menulis. – Sometimes I write.
Saya kadang menulis. – I sometimes write. (more casual / conversational)

Both are correct; kadang-kadang just sounds a bit more complete and standard.

Why is kadang-kadang written with a hyphen and repeated?

The repetition is called reduplication, very common in Indonesian. It can:

Mark plurality (e.g. buku-buku = books)
Soften or modify meaning (as with kadang-kadang)

Here, kadang alone already means sometimes, but kadang-kadang is the more typical form. The hyphen shows it is one unit, not two separate words.

Writing it as kadang kadang (with a space, no hyphen) is not standard.

Can I change the word order? For example: Saya kadang-kadang menulis fantasi singkat… Is that correct?

Yes, both word orders are correct, but the nuance is slightly different:

Kadang-kadang saya menulis fantasi singkat di buku harian sebelum tidur.
– Mild emphasis on kadang-kadang (on the frequency).
Saya kadang-kadang menulis fantasi singkat di buku harian sebelum tidur.
– Mild emphasis on saya (on the person; I sometimes write).

Both are natural. In everyday conversation, the second one (starting with Saya) is very common. The meaning in practice is basically the same.

Why menulis and not just tulis? What’s the difference?

Indonesian often uses a prefix me- on verbs.

tulis = base form (dictionary form, sometimes used as a command: Tulis! = Write!)
menulis = me-
- tulis → normal active verb: to write / writing

So:

Saya menulis fantasi singkat. – I write short fantasies.
Tulis fantasi singkat! – Write a short fantasy! (imperative)

In a normal sentence with a subject, you usually use the me- form (menulis), not the bare tulis.

Is there any difference between menulis and menuliskan?

There is a nuance:

menulis = to write (general, most common)
menuliskan = to write something down / write something for someone
- often emphasizes the result (what is written) or
- that you write for someone else’s benefit

In your sentence, menulis fantasi singkat is the most natural.
Menuliskan fantasi singkat sounds possible but a bit odd; it suggests more “to write down short fantasies (for someone)” and is not the usual way to describe what you do in your diary.

Does this sentence mean present tense, past tense, or a habit? How does Indonesian show tense here?

Indonesian does not mark tense on the verb the way English does.
Menulis can mean:

I write short fantasies (habitual)
I wrote short fantasies (in the past)
I am writing / was writing short fantasies (depending on context)

In this sentence, with kadang-kadang (“sometimes”), it naturally reads as a habitual action:

I sometimes write short fantasies in my diary before bed.

If needed, you can add time markers:

Dulu saya kadang-kadang menulis… – I used to sometimes write…
Sekarang saya kadang-kadang menulis… – Now I sometimes write…

What exactly does fantasi mean here? Is it like fantasy fiction or just imagination?

Fantasi is a loanword (from Dutch/English) and can mean:

Fantasy / imagination in general (daydreams, imagined scenes).
Fantasy stories as a genre (dragons, magic, etc.), depending on context.

In a diary context, menulis fantasi singkat usually suggests short imagined scenes, daydream-like pieces, or very short fantasy stories. If you wanted to make it clearly “fantasy stories,” you could say:

menulis cerita fantasi singkat – to write short fantasy stories

Why is it fantasi singkat and not singkat fantasi? Where do adjectives go?

In Indonesian, adjectives usually come after the noun they describe:

fantasi singkat = short fantasy / short fantasies
- fantasi = noun
- singkat = adjective (short)

Reversing them (singkat fantasi) is not normal Indonesian; it would sound wrong.

More examples:

buku baru – new book
cerita panjang – long story
film lucu – funny movie

What does buku harian literally mean, and how is it different from diary or journal in English?

Literally:

buku = book
harian = daily (from hari = day)

So buku harian = daily book, i.e. diary.

Usage:

buku harian = diary / personal journal (quite general)
jurnal in Indonesian is often used for:
- academic journals, research publications, or
- a more formal / specialized kind of journal

For an everyday personal diary, buku harian is the standard phrase.

Why is it di buku harian and not something else? Could I say di dalam buku harian?

Di is the basic preposition for in/at/on (location).

di buku harian = in the diary / in a diary
di dalam buku harian = literally “inside the diary,” a bit more explicit

Both are correct:

Saya menulis fantasi singkat di buku harian. – I write short fantasies in my diary.
Saya menulis fantasi singkat di dalam buku harian. – Emphasizes the “inside” idea a bit more, but still natural.

You would not normally use pada buku harian here; pada is more formal and suits abstract or official contexts better.

Why doesn’t it say buku harian saya? How do we know it’s “my” diary?

Indonesian often omits possessive words like “my” when the context is obvious.

buku harian = a diary / the diary (context-dependent)
buku harian saya = my diary (explicit)

In a typical personal statement about bedtime habits, it’s naturally understood that you mean your own diary, even if you don’t say saya.

If you want to be explicit, you can say:

Kadang-kadang saya menulis fantasi singkat di buku harian saya sebelum tidur.
– Sometimes I write short fantasies in my diary before bed.

What does sebelum tidur literally mean? Why is there no saya?

Literally:

sebelum = before
tidur = sleep / to sleep

So sebelum tidur = before sleeping / before (I) sleep.

Indonesian often drops the subject when it’s obvious from context. Here, since saya is the subject of the main verb (saya menulis), it’s automatically understood that saya is also the one who sleeps.

You could also say:

sebelum saya tidur – before I sleep
This is correct, slightly more explicit, but usually not necessary in a simple sentence like this.

Can I move sebelum tidur to the front of the sentence?

Yes. Indonesian is flexible with time expressions. These are all correct:

Sebelum tidur, saya kadang-kadang menulis fantasi singkat di buku harian.
Kadang-kadang saya menulis fantasi singkat di buku harian sebelum tidur.

Putting sebelum tidur at the front slightly emphasizes the time frame (Before bed, I sometimes write…), but the basic meaning does not change.

Why does the sentence use saya and not aku? What is the difference?

Both mean I / me, but differ in register:

saya
- Neutral, polite
- Used in formal situations and is always “safe”
aku
- More informal / intimate
- Used with friends, family, in songs, in casual writing

Your sentence with aku:

Kadang-kadang aku menulis fantasi singkat di buku harian sebelum tidur.

This would sound more personal and casual, like what someone might actually write in their diary or say to a close friend. Using saya keeps it neutral and a bit more formal.

Can I drop saya and just say Kadang-kadang menulis fantasi singkat…?

In this kind of sentence, you should not drop saya; it will sound incomplete or strange:

Kadang-kadang menulis fantasi singkat di buku harian sebelum tidur.
→ Feels like a fragment; the subject is missing.

Indonesian can omit the subject in some cases, especially in imperatives or where the subject is truly clear, but with a normal descriptive sentence about yourself, you keep saya or aku:

Kadang-kadang saya menulis…
Kadang-kadang aku menulis…

These are the natural forms.