Saya makan siang sendirian di kantin sekolah.

The sentence follows a very common Indonesian pattern:

Subject + predicate + adverb + place

• Saya = subject
• makan siang = predicate
• sendirian = adverb-like word describing how
• di kantin sekolah = place phrase

So the structure is very straightforward and natural in Indonesian.

In this sentence, makan siang is best understood as a fixed expression meaning to have lunch or eat lunch.

Literally:

• makan = eat
• siang = daytime / noon

But together, makan siang functions as one common phrase. So learners usually should not over-analyze siang here as a normal direct object. It is simply the standard way to say have lunch.

Compare:

• makan pagi / sarapan = have breakfast
• makan malam = have dinner

Because makan siang already works as a complete expression.

In English, eat often needs an object unless you mean eating in general. But in Indonesian, makan siang is a normal complete predicate by itself. You do not need to add another noun after it.

So this sentence is complete without anything else after makan siang.

Sendirian means alone or by oneself.

It is closely related to sendiri, which can also mean:

• alone
• oneself
• by oneself
• own

In this sentence, both are possible:

• Saya makan siang sendirian di kantin sekolah.
• Saya makan siang sendiri di kantin sekolah.

The difference is mostly nuance:

• sendirian often sounds a bit more explicitly alone
• sendiri is broader and very common

So sendirian emphasizes that the person was not with anyone.

Because here di is a preposition meaning in / at / on, so it is written as a separate word:

• di kantin = at the cafeteria
• di rumah = at home
• di sekolah = at school

This is different from di- as a passive prefix, which is written attached:

• dimakan = eaten / is eaten
• ditulis = written / is written

So:

• di kantin = correct
• dikantin = incorrect in this meaning

Indonesian usually puts the main noun first and the describing noun after it.

So:

• kantin sekolah = school cafeteria
• literally, cafeteria of the school

This is a very common pattern in Indonesian:

• buku bahasa = language book
• guru matematika = math teacher
• halaman sekolah = school yard

English often puts the describing noun first, but Indonesian usually puts it after the main noun.

It can mean either, depending on context.

Indonesian usually does not use articles like a, an, or the. So kantin sekolah can be interpreted from the situation.

In many contexts, it would naturally mean the school cafeteria, because the listener already knows which school cafeteria is meant.

If you want to be more specific, Indonesian can add words such as:

• sebuah kantin sekolah = a school cafeteria
• kantin sekolah itu = that school cafeteria / the school cafeteria

Yes. Indonesian verbs do not change form for tense the way English verbs do.

So Saya makan siang sendirian di kantin sekolah could mean different things depending on context:

• I have lunch alone in the school cafeteria
• I had lunch alone in the school cafeteria
• I eat lunch alone in the school cafeteria

If you want to make the time clearer, you can add time words:

• tadi = earlier
• kemarin = yesterday
• besok = tomorrow
• biasanya = usually
• sedang = currently/in the middle of

For example:

• Tadi saya makan siang sendirian di kantin sekolah.
• Biasanya saya makan siang sendirian di kantin sekolah.

Yes, aku is possible, but the tone changes.

• saya = neutral, polite, standard
• aku = more casual, personal, intimate

So:

• Saya makan siang sendirian di kantin sekolah. sounds neutral and standard.
• Aku makan siang sendirian di kantin sekolah. sounds more casual and conversational.

For learners, saya is usually the safer default in many situations.

Sometimes, yes, especially in casual conversation when the subject is already clear.

For example, if someone asks:

• Makan siang di mana? = Where did you have lunch?

You could answer:

• Makan siang sendirian di kantin sekolah.

But as a full standalone sentence, keeping saya is the clearest and most standard choice.

Yes, Indonesian word order is somewhat flexible, especially with adverbs and place phrases.

The original sentence is very natural:

• Saya makan siang sendirian di kantin sekolah.

But these are also possible:

• Saya makan siang di kantin sekolah sendirian.
• Di kantin sekolah, saya makan siang sendirian.

The differences are mainly about emphasis:

• putting di kantin sekolah first emphasizes the location
• keeping sendirian before the place sounds very natural and balanced

It can correspond to either in or at in English.

The Indonesian preposition di is broader than English in or at. It marks location in a general way, and English chooses the best preposition based on natural usage.

So di kantin sekolah can be understood as:

• in the school cafeteria
• at the school cafeteria

In most English translations, in the school cafeteria is the most natural.