Learn Hardcore Indonesian: Saya sedang mengerjakan tugas di perpustakaan.

Saya mengerjakan tugas di perpustakaan.
= I do / I am doing my assignment at the library. (neutral: could be general or now, depending on context)
Saya sedang mengerjakan tugas di perpustakaan.
= I am in the middle of doing my assignment at the library (right now / around this moment).

It is similar to the English present continuous (am doing), but it is an optional word that you add to make the “ongoing right now” meaning explicit.

Can I leave out sedang? Will the sentence still be correct?

Yes, you can leave out sedang, and the sentence is still grammatically correct:

Saya mengerjakan tugas di perpustakaan.

Without sedang, the sentence can mean:

a general habit: I (usually) do my assignments at the library.
or a present action: I am doing my assignment at the library (right now).

Context will decide which one people understand. Sedang is just there to make the “right now, in progress” meaning clearer.

What is the difference between mengerjakan and kerja / bekerja?

The base word is kerja (work).

kerja (noun/verb, informal): work / to work
- Saya kerja di Jakarta. = I work in Jakarta. (informal)
bekerja (verb): to work (intransitive: no direct object)
- Saya bekerja di Jakarta. = I work in Jakarta.
mengerjakan (verb): to do / to work on something (transitive: needs an object)
- Saya mengerjakan tugas. = I do / I am doing the assignment.

So you say:

mengerjakan tugas = do an assignment / do homework
but bekerja di kantor = work at the office

You cannot replace mengerjakan with bekerja in this sentence, because you are not “working” in general; you are doing a specific thing (your assignment).

Why is it mengerjakan, not mengerja or something shorter?

Indonesian uses affixes to change word class and meaning.

Root: kerja (work)
With meN- (verb, usually “to do X”): meng-
- kerja → mengerja-
With -kan (often makes it transitive / “do [something] to something else”): mengerja-
- -kan → mengerjakan

So mengerjakan literally means “to do (some work) on something” → “to do, to work on (an assignment, a task, etc.)”.

The form mengerja is basically just an intermediate form; in normal usage you say mengerjakan.

Does mengerjakan always need an object, like tugas?

Yes. Mengerjakan is a transitive verb: it expects a direct object.

Saya sedang mengerjakan tugas. ✅ (I am doing what? → tugas)
Saya sedang mengerjakan. ❌ (sounds incomplete)

If you do not want to mention the object, you’d normally switch to a verb that doesn’t need one, like bekerja (to work):

Saya sedang bekerja di perpustakaan. = I am working at the library.

What exactly does tugas mean here? Does it mean “homework”?

Tugas is a general word for task, assignment, duty.

In a school or university context:

tugas often means assignment / homework / coursework.
tugas rumah or pekerjaan rumah (PR) is more clearly “homework”.

In conversation, if a student says:

Saya sedang mengerjakan tugas.

listeners will usually understand it as “I’m doing my assignment / homework,” unless context suggests some other kind of task (e.g., job task).

Can I change the word order, like Di perpustakaan saya sedang mengerjakan tugas?

Yes, that is also correct:

Saya sedang mengerjakan tugas di perpustakaan.
Di perpustakaan saya sedang mengerjakan tugas.

Both are grammatical and mean the same thing.

Differences:

The original emphasizes what you’re doing (doing an assignment) and then adds where at the end.
Di perpustakaan saya sedang mengerjakan tugas puts more emphasis on the location (at the library) first, which can be useful if:
- you are contrasting locations, or
- you want to set the scene: “At the library, I am doing my assignment.”

In everyday speech, the original order (subject–verb–object–place) is more common, but both are natural.

Can I drop saya and just say Sedang mengerjakan tugas di perpustakaan?

Yes, in the right context.

Indonesian often drops the subject pronoun when it is clear from context who the subject is. For example, in a chat message where it is obvious you are talking about yourself:

Sedang mengerjakan tugas di perpustakaan.

would be understood as “(I’m) doing my assignment at the library.”

However:

In formal writing or when context is not clear, it is safer and more natural to keep saya.
Spoken Indonesian, especially casual conversation, drops pronouns much more often than formal Indonesian.

Is saya formal? Could I say Aku sedang mengerjakan tugas di perpustakaan?

Both are correct, but they differ in formality and who you’re talking to:

saya: neutral–polite, used in most formal or semi-formal situations, with strangers, teachers, superiors, etc.
aku: informal/intimate, used with friends, family, or people your own age in casual settings (depending on region and relationship).

So:

To a teacher: Saya sedang mengerjakan tugas di perpustakaan. (best)
To a close friend: Aku lagi ngerjain tugas di perpus. (very casual, also using informal forms)

The choice of saya vs aku should match how close you are to the listener and how formal the situation is.

Why is it di perpustakaan and not something like ke perpustakaan?

Indonesian uses different prepositions for different relationships:

di = at / in / on (location, where something is)
- di perpustakaan = at the library / in the library
ke = to (movement toward a place)
- ke perpustakaan = to the library
dari = from (movement from a place)
- dari perpustakaan = from the library

In your sentence you are describing where you are doing the task, not movement, so di is the correct choice:

Saya sedang mengerjakan tugas di perpustakaan. ✅
Saya sedang mengerjakan tugas ke perpustakaan. ❌ (ungrammatical)

How would I say “I do my assignments at the library every day” (a habit, not right now)?

You can say:

Saya mengerjakan tugas di perpustakaan setiap hari.

Notes:

No sedang, because you are talking about a habitual action, not an action in progress at this moment.
setiap hari = every day.
If you say Saya sedang mengerjakan tugas di perpustakaan setiap hari, it sounds odd, because sedang (“right now”) clashes with setiap hari (“every day, habit”).

Is there a more casual way to say this sentence in spoken Indonesian?

Yes, everyday spoken Indonesian often uses more informal forms:

Aku lagi ngerjain tugas di perpus.

Changes:

saya → aku (more intimate)
sedang → lagi (very common informal progressive marker)
mengerjakan → ngerjain (informal, from mengerjakan, dropping some sounds)
perpustakaan → perpus (common shortened form)

Meaning is the same, but the tone is much more casual and common in conversation among friends.

Is perpustakaan only for libraries with books, or can it be any study place?

Perpustakaan specifically means library, usually a place where books (and sometimes other materials) are collected and can be read or borrowed.

For a more general study place, people might say:

ruang belajar = study room
tempat belajar = place to study
coworking space (often said as-is in Indonesian)

But perpustakaan itself is understood as a library, not just any study area.