Learn Hardcore Indonesian: Saya menaruh buku di kotak.

Saya – more formal, polite, neutral; safe for talking to strangers, teachers, in work, etc.
Aku – more informal/intimate; used with friends, family, people your age or younger.

The rest of the sentence stays the same. The choice between saya and aku depends on social context, not on grammar.

Why is there no word for “the” or “a” before buku and kotak?

Indonesian normally has no separate words for “the” or “a/an”. Nouns are usually bare:

buku can mean a book or the book
kotak can mean a box or the box

Context tells you whether it’s specific or not. If you really want to emphasize one book / one box, you can add sebuah:

Saya menaruh sebuah buku di sebuah kotak.
(I put a/one book in a/one box.)

But usually the simple form buku, kotak is enough.

How do I show plural, like “books” or “boxes”, in this kind of sentence?

There is no automatic -s ending in Indonesian. Common ways to show plural:

Use a number + classifier
- Saya menaruh tiga buku di kotak. – I put three books in the box.
- Saya menaruh beberapa buku di kotak. – I put several books in the box.
Reduplication (more common in some contexts)
- buku-buku – books
- kotak-kotak – boxes
- Saya menaruh buku-buku di kotak.
Rely on context
Often speakers don’t mark plural at all; listeners infer it from context.

What’s the difference between di kotak and ke dalam kotak?

di kotak = in the box / at the box (focus: location, “where it is”)
ke dalam kotak = into the box (focus: movement into the interior)

So:

Saya menaruh buku di kotak.
– Neutral: “I put the book in the box.” (We understand that it ends up there.)
Saya menaruh buku ke dalam kotak.
– Emphasizes the motion of putting it into the inside of the box.

Both are grammatical; the first is shorter and very natural.

Is the word order fixed? Can I say Saya menaruh di kotak buku instead?

The basic Indonesian word order is Subject – Verb – Object – (Place/Time):

Saya (S) menaruh (V) buku (O) di kotak (Place).

If you say:

Saya menaruh di kotak buku.

this sounds odd because buku is now after di kotak, so it looks like buku is modifying kotak:

kotak buku = book box / box for books

So Saya menaruh di kotak buku is interpreted more like:
I put (something unstated) in the book box.

To keep buku as the object, it should come before the place phrase:

Saya menaruh buku di kotak. ✅

Can I drop Saya and just say Menaruh buku di kotak?

In normal Indonesian, you generally need a subject. Just saying:

Menaruh buku di kotak.

feels incomplete or like a fragment (similar to saying “Put the book in the box.” as a command in English).

However, as a command, you’d change the form a bit:

Taruh buku di kotak. – Put the book in the box.
(Here the subject “you” is implied.)

For a regular statement, keep Saya (or Aku or another subject):

Saya menaruh buku di kotak. – I put the book in the box.

Is the sentence about the past, present, or future? How do I show tense in Indonesian?

Indonesian verbs do not change form for tense.
Saya menaruh buku di kotak. by itself can mean:

I put the book in the box. (past)
I am putting the book in the box. (present)
I will put the book in the box. (future, in some contexts)

To be clear, you add time words or aspect markers:

Past: tadi, kemarin, sudah
- Saya tadi menaruh buku di kotak. – I put the book in the box earlier.
- Saya sudah menaruh buku di kotak. – I have (already) put the book in the box.
Future: nanti, akan
- Saya akan menaruh buku di kotak. – I will put the book in the box.

Context almost always clarifies the time.

When should I use menaruh vs meletakkan or memasukkan?

All can be translated as “to put/place”, but there are nuances:

menaruh – to put/place something somewhere (very general).
meletakkan – to put/place something down, usually on a surface (table, floor, shelf, etc.).
memasukkan – to put something into something (into a box, bag, room, etc.).

With kotak (a box):

Saya menaruh buku di kotak. – I put the book in the box. (neutral)
Saya memasukkan buku ke dalam kotak. – I put the book into the box. (emphasis on “into”)

Meletakkan is more natural with on-type locations:

Saya meletakkan buku di meja. – I put the book on the table.

Is di here a preposition or the passive prefix di-?

In Saya menaruh buku di kotak, di is a preposition meaning in/at/on (depending on the noun).

The passive prefix di- attaches directly to a verb (without a space):

ditaruh – is/was put
diletakkan – is/was placed

So:

di kotak (with a space) = preposition + noun (“in the box”)
ditaruh (no space) = passive verb (“is put / was put”)

Do I need a classifier like sebuah before buku or kotak?

You don’t need it. Bare nouns are perfectly natural:

Saya menaruh buku di kotak.

You usually add sebuah (or another classifier) when you want to emphasize one item or sound a bit more descriptive:

Saya menaruh sebuah buku di dalam sebuah kotak besar.
– I put a book into a big box.

For everyday speech, it’s very common to leave classifiers out unless number is important.

Is Saya menaruh buku di kotak natural in everyday conversation, or would Indonesians say something else?

It’s grammatically correct and understandable, but in casual spoken Indonesian you often hear slightly more colloquial patterns, for example:

Aku taruh bukunya di kotak.
– Using aku and taruh, and -nya to show “the book / that book”.

or just:

Bukunya aku taruh di kotak.
– Fronting bukunya for focus: “The book, I put (it) in the box.”

So your sentence is fine, especially in neutral or slightly formal contexts. In relaxed speech, people often:

use aku instead of saya
drop meN- (taruh instead of menaruh)
add -nya to make the noun definite.

How would I say “The book was put in the box by me” (passive form) in Indonesian?

A common passive version is:

Buku itu ditaruh di kotak oleh saya.

Breakdown:

Buku itu – the book
ditaruh – was put (passive)
di kotak – in the box
oleh saya – by me

In everyday Indonesian, people often omit oleh saya when it’s obvious who did it:

Buku itu ditaruh di kotak. – The book was put in the box.

Are there particles or small words I could add to sound more natural, like softening the sentence?

Yes, depending on context you might add:

dulu – “first / for now”
- Saya taruh buku di kotak dulu.
  – I’ll just put the book in the box for now.
ya – softening/confirming, at the end of a sentence
- Saya taruh buku di kotak, ya.
  – I’ll put the book in the box, OK?
saja / aja – “just / only” (aja = casual form)
- Saya taruh buku di kotak saja.
  – I’ll just put the book in the box (and not somewhere else).

These don’t change the core grammar, but they add natural nuance in conversation.