Learn Hardcore Indonesian: Saya menaruh buku di atas meja.

The verb menaruh means to put or place. Its root is taruh. The prefix meN- attaches to the root and, because the root starts with t, the t drops and the prefix surfaces as men- → menaruh. In casual speech you will also hear taruh used without the prefix (for example, Saya taruh …) or the colloquial contraction naruh (for example, Aku naruh …).

Is this past, present, or future? How do I show time in Indonesian?

Indonesian verbs don’t inflect for tense. The sentence can be past, present, or future depending on context or time words:

Past/completed: Saya sudah menaruh buku di atas meja. (I have already put…)
Recent past: Tadi saya menaruh buku di atas meja. (Earlier I put…)
Future: Saya akan menaruh buku di atas meja. (I will put…)
Ongoing: Saya sedang menaruh buku di atas meja. (I am in the middle of putting…)

Why is there no article like a or the? How can I say a book or the book?

Indonesian has no articles. You add words or clitics to express definiteness/indefiniteness:

Indefinite (a book): Saya menaruh sebuah buku / satu buku di atas meja.
Definite (the book): Saya menaruh buku itu di atas meja. or Saya menaruh bukunya di atas meja. Note: -nya can mean the specific/previously known item (the book) or his/her book, depending on context.

Is buku singular or plural here? How do I make it explicitly plural?

Bare buku can be singular or plural from context. To make it explicit:

Plural via reduplication: buku-buku
With quantifiers: beberapa buku (several books), banyak buku (many books), dua buku (two books)

What’s the difference between di atas meja and di meja?

Both can be used with placement verbs, but there’s a nuance:

di atas meja emphasizes on top of the table’s surface.
di meja is common in speech and can mean on the table or at the table, depending on context. If you want to be precise about the surface, di atas meja is clearer.

Should I use di atas or ke atas when describing placing something onto the table?

Use di atas with placement verbs to indicate the final location: Saya menaruh buku di atas meja. Ke atas emphasizes upward movement and is uncommon/natural only in specific contexts. People nearly always say di atas meja for onto the table after verbs like taruh/letakkan.

Is di atas one word or two? I see diatas sometimes.

Write the location preposition as two words: di atas. The single word diatas is nonstandard in this meaning. Contrast this with the passive prefix di- on verbs, which attaches directly (for example, ditaruh, not di taruh).

Can I drop the subject Saya? What are colloquial alternatives?

Yes, subjects are often omitted if clear from context, though for a complete neutral sentence it’s common to keep Saya. Colloquial options:

Saya taruh buku di atas meja. (dropping the prefix)
Aku naruh buku di atas meja. (informal pronoun and colloquial verb) For a command, simply say Taruh bukunya di atas meja.

Can I use other verbs like meletakkan or menempatkan instead of menaruh?

meletakkan is a close synonym for physical placement and is very common: Saya meletakkan buku di atas meja.
menempatkan is more formal/abstract, often about assigning positions or placing things systematically. For a single book on a table, menempatkan can sound overly formal or odd; prefer menaruh or meletakkan.

How do I say this in the passive or with the object first?

Several natural options:

Passive with di-: Buku itu ditaruh di atas meja (oleh saya). (oleh saya is usually omitted)
Object-fronting (colloquial passive-like): Buku itu saya taruh di atas meja.
Active (original): Saya menaruh buku itu di atas meja.

Does menaruh require an object? What if it’s understood from context?

Yes, menaruh is transitive and normally takes an object. If the object is understood, use a pronoun or the clitic -nya:

Saya menaruhnya di atas meja. (I put it on the table) Using Saya menaruh di atas meja without an object feels incomplete in standard usage.

How do I say The book is on the table?

Just use a noun plus the location phrase (no verb needed):

Buku di atas meja.
More specific: Buku itu di atas meja. or Bukunya di atas meja.