Learn Hardcore Indonesian: Saya belajar di perpustakaan untuk ujian matematika. - I study in the library for the math exam.

The original sentence slightly emphasizes where you study (the library), then why (for the exam).
The rearranged version slightly emphasizes why you study (for the exam), then where.

In everyday conversation, both sound natural. Indonesian word order is fairly flexible as long as you keep phrases together and the meaning stays clear.

How do I know if this means I study, I am studying, or I studied? There’s no tense marking.

Indonesian verbs usually do not change for tense. The sentence:

Saya belajar di perpustakaan untuk ujian matematika.

can mean:

I study at the library for the math exam.
I am studying at the library for the math exam.
I studied at the library for the math exam.

The exact meaning depends on context or on extra time words:

Tadi – earlier:
Tadi saya belajar di perpustakaan untuk ujian matematika.
→ I studied earlier at the library…
Sekarang – now:
Sekarang saya belajar di perpustakaan untuk ujian matematika.
→ I’m studying now at the library…
Nanti / besok – later / tomorrow:
Besok saya belajar di perpustakaan untuk ujian matematika.
→ Tomorrow I will study at the library…

You can also add sedang to emphasize an ongoing action (see another question below).

Does di here mean in, at, or on? Why is it di perpustakaan and not something else?

di is a location preposition. In English, it often corresponds to in, at, or on, depending on context.

di perpustakaan = in/at the library

Indonesian doesn’t distinguish as strictly between in and at as English does. di is used for a static location:

di rumah – at home
di sekolah – at school
di kantor – at the office

Compare with ke, which indicates movement to somewhere:

Saya pergi ke perpustakaan. – I go to the library.
Saya belajar di perpustakaan. – I study at/in the library.

So di = being there; ke = going there.

What is the difference between saya and aku? Could I say Aku belajar di perpustakaan… instead?

Both saya and aku mean I / me, but they differ in formality and register:

Saya: more formal or neutral.
- Used in school, work, with strangers, in writing, in polite conversation.
Aku: more informal / intimate.
- Used with close friends, family, or in casual contexts, songs, social media.

So:

Saya belajar di perpustakaan untuk ujian matematika. – neutral, polite.
Aku belajar di perpustakaan untuk ujian matematika. – casual, friendly.

Grammatically both are fine; choose based on who you’re talking to and the situation.

Can I drop saya and just say Belajar di perpustakaan untuk ujian matematika?

Yes, you canomit saya in the right context. Indonesian often drops subject pronouns when it’s clear who is being talked about.

Belajar di perpustakaan untuk ujian matematika.

This might appear:

In notes or messages to yourself.
As a heading or bullet point (e.g., a study plan).
In conversation, if the subject is obvious from context.

However, in a full, neutral sentence—especially if it’s the first time you mention it—Saya belajar… is clearer and more natural.

Why is it ujian matematika and not matematika ujian? How does noun order work here?

Indonesian typically puts the main noun first, and the modifying noun after it.

ujian matematika
- ujian = exam/test (main noun)
- matematika = mathematics (modifier)
  → literally: exam of mathematics = math exam

If you said matematika ujian, it would sound wrong or at least unnatural; it doesn’t follow standard noun phrase order.

Other examples:

buku sejarah – history book (book of history)
guru bahasa Inggris – English teacher (teacher of English)
pelajaran matematika – math lesson/class

Is there any difference between ujian and tes? Which one fits better here?

Both are used, but with slightly different typical uses and feel:

ujian
- More formal, common in schools/universities.
- Often refers to official exams: midterms, finals, national exams.
tes
- Borrowed from English test.
- Used in many contexts: school, medical tests, job tests, language tests, etc.
- Slightly more informal in some contexts, but still very common.

In your sentence:

Saya belajar di perpustakaan untuk ujian matematika. – Very natural, sounds like a school/university exam.
Saya belajar di perpustakaan untuk tes matematika. – Also understandable and acceptable, maybe a bit more general.

For a student talking about a scheduled school exam, ujian matematika is a perfect choice.

What exactly does untuk mean here? Could I use buat instead?

untuk generally means for (purpose, benefit, or target):

Saya belajar … untuk ujian matematika.
→ I study … for the math exam.

buat is a more informal alternative, especially in spoken Indonesian:

Saya belajar di perpustakaan buat ujian matematika.

Differences:

untuk – more formal/neutral; good for writing, polite speech, school contexts.
buat – casual; common in everyday conversation with friends or family.

Meaning-wise, in this sentence they are the same.

Does di perpustakaan mean in the library or at the library? Which is more accurate?

di perpustakaan can correspond to either in the library or at the library in English:

If you imagine yourself inside the building: in the library.
If you think more generally about the place as a location: at the library.

Indonesian doesn’t always make the same distinction as English. If you want to really emphasize inside, you can say:

di dalam perpustakaan – inside the library

But in most cases, di perpustakaan is enough and natural.

How can I specifically say I am (currently) studying rather than just I study?

To emphasize that the action is in progress right now, you can add sedang before the verb:

Saya sedang belajar di perpustakaan untuk ujian matematika.

This clearly suggests:

I am studying at the library for the math exam (right now / currently).

You can also use time words:

Sekarang saya belajar di perpustakaan… – Now I’m studying at the library…

But sedang is the most direct way to mark a progressive aspect like English -ing.

What is the root word of perpustakaan? How is this word built?

Perpustakaan is built from:

buku – book
pustaka – a more literary/formal word related to books / writings (comes from Sanskrit)
per-…-an – a prefix-suffix pair that can form nouns indicating places or abstract concepts

So:

pustaka → related to books
perpustakaan → a place related to books = library

You don’t normally say pustaka in everyday speech by itself, but perpustakaan is very common and standard for library.

If I want to say I will study at the library for the math exam, do I need to change belajar?

You don’t change belajar itself, but you can add a time marker or a future marker:

Ways to show future:

Use time words:
- Besok saya belajar di perpustakaan untuk ujian matematika.
  → Tomorrow I will study…
Use akan (future marker):
- Saya akan belajar di perpustakaan untuk ujian matematika.
  → I will study at the library for the math exam.
Combine both for clarity:
- Besok saya akan belajar di perpustakaan untuk ujian matematika.

The verb belajar itself stays the same; tense is expressed through extra words and context.

How would I make math exams (plural) instead of just math exam?

Indonesian usually doesn’t mark plural with word changes unless needed for clarity. Context often tells you whether it’s singular or plural.

Saya belajar untuk ujian matematika.
→ could mean for the math exam or for math exams depending on context.

If you really need to emphasize plural:

ujian-ujian matematika – math exams (reduplication of ujian)
beberapa ujian matematika – several math exams
banyak ujian matematika – many math exams

Example:

Saya belajar di perpustakaan untuk beberapa ujian matematika.
→ I study at the library for several math exams.