Learn Hardcore Indonesian: Saya menitipkan kunci ke tetangga karena ada urusan keluarga. - I leave the key with the neighbor because of a family matter.

titip = to entrust/leave something with someone for safekeeping (temporary; you expect it back).
menitipkan = the formal/transitive form of titip; pattern: menitipkan [thing] (kepada/ke) [person].
memberikan = to give (transfer possession), not necessarily temporary.
Morphology: meN- + titip + -kan → menitipkan. The initial t of titip drops after meN- (standard sound change), leaving menitip-, then add -kan.

Why is ke used before tetangga? Can I use kepada, pada, or sama?

All are possible with slightly different register:
- Formal/standard: menitipkan X kepada/pada Y.
- Everyday speech: titip/menitipkan X ke Y (very common).
- Very colloquial: titip X sama Y.
In careful writing, prefer kepada when the “destination” is a person.

Can I drop -kan and just say Saya titip kunci ke tetangga?

Yes. Saya titip kunci ke tetangga is natural and a bit more casual.
Very casual speech often uses nitip or the colloquial suffix -in: Saya nitip/titipin kunci ke tetangga.

What’s the difference between menitipkan and menitipi?

With -kan, the direct object is the thing: Saya menitipkan kunci kepada tetangga.
With -i, the direct object is the recipient/place: Saya menitipi tetangga kunci (grammatical but rare/old-fashioned).
In practice, speakers prefer either the -kan version or a passive with -i on the recipient: Tetangga saya dititipi kunci.

How would I say this in the passive?

Long passive (di-): Kunci dititipkan ke/kepada tetangga (oleh saya) karena ada urusan keluarga.
Short passive/topicalization: Kunci saya titipkan ke tetangga karena ada urusan keluarga. Both are common; the short version sounds very natural.

Do I need to say tetangga saya to mean my neighbor?

tetangga by itself is ambiguous (a/the neighbor). Indonesian doesn’t mark definiteness.
To be explicit: tetangga saya (my neighbor), tetangga itu (that/the neighbor), or seorang tetangga (a neighbor, introducing someone).
If you mean the neighbor’s place: ke rumah tetangga.

Is kunci singular or plural here? How do I make it clear?

kunci could be one or many; context decides.
To specify:
- One: satu/sebuah kunci.
- Several: beberapa kunci, dua/3 dst. kunci.
- Reduplication (kunci-kunci) is possible but less common than using numbers/quantifiers.

How do I show past, present, or future time?

Indonesian is tenseless; add time/aspect words:
- Past/completed: sudah, tadi, kemarin, barusan.
- Future/intended: akan, nanti, mau (about to/intend).
Example: Saya sudah menitipkan kunci…, Saya akan menitipkan kunci….

Why use ada in karena ada urusan keluarga? Could I say saya punya?

ada is existential (“there is/are”), a neutral way to state a reason: “because there is a family matter.”
saya punya urusan keluarga sounds a bit more personal/possessive and is also fine in speech.
You can also say karena saya ada urusan keluarga; adding the subject is optional.

What’s the nuance difference between urusan keluarga, masalah keluarga, and acara keluarga?

urusan keluarga = family matter/affair (neutral; often used as a polite reason).
masalah keluarga = a family problem (implies difficulty/issue).
acara keluarga = a family event/occasion (e.g., gathering, ceremony).

Is karena the only way to say “because”? What about sebab or gara-gara?

karena = neutral, most common.
sebab = more formal/literary; interchangeable with karena in meaning.
gara-gara = colloquial and often implies blame/negative cause; avoid in neutral/formal contexts.

Can I put the reason first? Do I need a comma?

Yes: Karena ada urusan keluarga, saya menitipkan kunci ke tetangga.
When the reason clause comes first, use a comma. When it comes after, a comma is usually omitted.

Should it be ke tetangga or ke rumah tetangga?

ke tetangga focuses on the recipient (the person).
ke rumah tetangga specifies the location (to the neighbor’s house). Use this if you want to emphasize where you left the key.

How do I avoid repeating kunci if it’s already known?

Use the clitic -nya: Saya menitipkannya ke tetangga… Here, -nya replaces “the key” that’s understood from context.