Learn Hardcore Indonesian: Saya belajar di perpustakaan, lalu pulang ke rumah.

The saya in the first clause is understood to still be the subject in the second clause.
Repeating saya is grammatically correct but sounds a bit heavier or more emphatic:

Saya belajar di perpustakaan, lalu saya pulang ke rumah. (also correct)

What exactly does “lalu” mean here? Is it like “and” or “then”?

Lalu is a connector that usually means “then” or “and then”, showing sequence of actions.

It tells you that pulang ke rumah happened after belajar di perpustakaan.
It’s a bit more narrative than just “and”.

Similar words you might see:

kemudian = then / afterwards (slightly more formal)
lalu = then / and then (very common, neutral)
terus = then / and then / keep (more informal, conversational)

So:

Saya belajar di perpustakaan, lalu pulang ke rumah.
≈ “I studied at the library, then went home.”

Why is it “belajar di perpustakaan” but “pulang ke rumah”? Why di in one place and ke in the other?

Because di and ke express different things:

di = at / in / on (location, where something happens)
ke = to / toward (direction, where you are going)

In the sentence:

belajar di perpustakaan = study at the library (location of the action)
pulang ke rumah = go home / return to home (direction of movement)

You normally say:

di
- place: di sekolah, di kantor, di perpustakaan
ke
- place: pergi ke sekolah, datang ke kantor, pulang ke rumah

Does “pulang” already mean “go home”? Why do we still need “ke rumah”?

Pulang by itself means “to go back” / “to return (home/one’s place)”.

In many contexts, pulang alone is enough, because “home” is understood:
- Sudah malam, saya pulang. = It’s already late, I’m going (home).

Adding ke rumah:

Makes it explicitly “return to (the) house/home”.
Is very natural and common, especially in simple sentences like this.

So both:

Saya pulang.
Saya pulang ke rumah.

are correct. The second is just more explicit about “home”.

Do I need to say “rumah saya” (my house), or is “ke rumah” enough?

Ke rumah by default is understood as “to (my/our) home” when the subject is you.

Saya pulang ke rumah. = I go home (to my home).
Dia pulang ke rumah. = He/She goes home (to his/her home).

If you want to be extra explicit, you can say:

Saya pulang ke rumah saya.
But in everyday Indonesian this sounds a bit redundant unless you are contrasting with someone else’s house.

To talk about someone else’s home:

Saya pulang ke rumah teman saya. = I go back to my friend’s house.
Dia pulang ke rumah orang tuanya. = He/She goes back to his/her parents’ house.

Is “Saya belajar di perpustakaan, lalu pulang ke rumah” past tense, present, or future?

Indonesian verbs do not change form for tense. The base form belajar, pulang can mean past, present, or future. The tense is understood from context or time words.

This sentence, by itself, could be:

Past: “I studied at the library, then went home.”
Habitual: “I study at the library, then go home.”
Future (with context): “Later I will study at the library, then (will) go home.”

To make it clearly past, you might add:

Tadi (earlier): Tadi saya belajar di perpustakaan, lalu pulang ke rumah.

To make it clearly future:

Nanti (later): Nanti saya belajar di perpustakaan, lalu pulang ke rumah.

Can I drop “Saya” and just say “Belajar di perpustakaan, lalu pulang ke rumah”?

Yes, in the right context. Indonesian often omits the subject if it’s obvious from the situation or earlier conversation.

(Saya) belajar di perpustakaan, lalu (saya) pulang ke rumah.

Dropping saya like that sounds like you’re describing your routine, a note, or a caption. In isolation, though, including Saya is clearer for learners and standard in full sentences.

Is the word order fixed? Can I say “Saya di perpustakaan belajar, lalu pulang ke rumah”?

The neutral, most natural order is:

Saya belajar di perpustakaan… (Subject – Verb – Place)

Saya di perpustakaan belajar is understandable, but it sounds less natural in this simple sentence and might feel like you’re emphasizing the place unusually.

In general:

Action verb + di
- place is the usual pattern:
  makan di restoran, bekerja di kantor, belajar di perpustakaan.

So for everyday speech and writing, stick with:

Saya belajar di perpustakaan, lalu pulang ke rumah.

Could I use “kemudian” or “terus” instead of “lalu”?

Yes, with slight differences in style:

kemudian – “then / afterwards”, slightly more formal or written:
- Saya belajar di perpustakaan, kemudian pulang ke rumah.
lalu – “then / and then”, neutral and very common:
- Saya belajar di perpustakaan, lalu pulang ke rumah.
terus – “then / and then / keep on”, informal, conversational:
- Saya belajar di perpustakaan, terus pulang ke rumah.

All three are understandable; lalu and kemudian are safer for neutral standard Indonesian.

Why do we use “di perpustakaan”? Can we just say “Saya belajar perpustakaan”?

You need the preposition di to show location.

perpustakaan = library (the noun, the place)
di perpustakaan = at the library (location phrase)

Saya belajar perpustakaan would be interpreted as “I study library” (like “library science”), which is wrong here. To express “at the library”, you must say:

Saya belajar di perpustakaan.

Does “perpustakaan” need “the” in Indonesian, like “the library”?

Indonesian does not have articles like “a” or “the”. Perpustakaan can mean “a library” or “the library”, depending on context.

So:

Saya belajar di perpustakaan.
can be translated as:
“I study at the library.”
“I study at a library.”

English must choose; Indonesian doesn’t mark that difference in the noun itself.

What is the politeness or formality level of this sentence?

The sentence is neutral and standard. It’s appropriate for:

speaking with friends
speaking with teachers
writing simple compositions or messages

If you switched saya to another pronoun, the politeness level could change (for example, aku, gue, saya, kami), but with saya, the sentence is politely neutral.