Learn Hardcore Indonesian: Tetangga saya sempat curiga ketika melihat orang asing di depan rumah. - My neighbor was briefly suspicious when seeing a stranger in front of the house.

the suspicion was temporary, and/or
something happened in between that allowed that suspicion to arise (they got the chance to feel suspicious).

It doesn’t mean “had time” in a literal sense here; it’s more about a short, completed state in the past.

Could I just say Tetangga saya curiga without sempat? How would the meaning change?

Yes, you can say:

Tetangga saya curiga ketika melihat orang asing di depan rumah.

The difference:

With sempat:
⇒ implies the suspicion was brief / momentary, or that it happened but is now over.
Without sempat:
⇒ simply states that your neighbor was suspicious when seeing the stranger, with no extra nuance about duration or “having the chance.”

Both are correct; sempat just softens and specifies the aspect of the event.

I learned sempat as “had time to.” Does it still mean that here?

It’s the same word, but the nuance shifts depending on context.

Had time / managed to (do something)
- Saya sempat makan sebelum rapat.
  → I had time to eat / I managed to eat before the meeting.
Briefly / at one point (a state or action that happened and is over)
- Tetangga saya sempat curiga.
  → My neighbor was briefly / at one point suspicious.

So the core idea of sempat is:
→ something did happen, but it’s seen as limited, brief, or just one occurrence.
Here it doesn’t mean “had time” literally; it’s more like “did briefly become (suspicious).”

Why is it curiga and not mencurigai? What’s the difference?

Curiga = suspicious (adjective / stative verb: a state or feeling)
Mencurigai = to suspect (someone/something) (active verb that takes an object)

In your sentence:

Tetangga saya sempat curiga
= My neighbor was (briefly) suspicious → describing the neighbor’s feeling/state.

If you say:

Tetangga saya sempat mencurigai orang asing itu.
= My neighbor (briefly) suspected that stranger.
Here, orang asing itu is the object of mencurigai.

So:

Use curiga to describe someone’s state.
Use mencurigai when you explicitly say whom they suspect.

Is curiga an adjective or a verb in Indonesian?

It behaves like both, depending on how you think about it:

Functionally, it’s like an adjective:
Dia curiga. → He/She is suspicious.
Grammatically in Indonesian, many adjectives can act like stative verbs (verbs that describe a state). They don’t need “to be”:
- Dia curiga. (literally: He/She suspicious.)
- Dia marah. → He/She is angry.
- Dia sedih. → He/She is sad.

In your sentence, curiga is describing a state: the neighbor was in a suspicious state.

Who is doing the seeing in ketika melihat orang asing? Why is there no subject like dia?

The subject is understood from context: it’s still tetangga saya.

Full, explicit version:

Tetangga saya sempat curiga ketika dia melihat orang asing di depan rumah.

In Indonesian, when the subject of the main clause and the subordinate clause is the same, the second subject is often dropped:

Saya kaget ketika melihat anjing besar.
→ subject of melihat is understood to be saya.

So in your sentence, ketika melihat is understood as when (my neighbor) saw.

What’s the difference between ketika, saat, and waktu here? Could I replace ketika?

All three can introduce a “when” clause, and all three would work here:

ketika melihat orang asing...
saat melihat orang asing...
waktu melihat orang asing...

Nuance (general tendencies; there is overlap):

ketika
- Slightly more neutral / standard.
- Common in both spoken and written Indonesian.
saat
- Also neutral; maybe a bit more formal in some contexts.
- Very common in news and written language, but also used in speech.
waktu
- Originally means time; in this use it’s more colloquial / conversational as “when.”

In everyday speech, all three are widely used. Here, ketika is a perfectly natural choice.

Does orang asing mean “foreigner” or “stranger”?

Literally:

orang = person
asing = foreign / unfamiliar

So orang asing can mean:

Foreigner (someone from another country)
Stranger (someone unknown to you)

Which one is meant depends on context. In your sentence:

...ketika melihat orang asing di depan rumah.
likely means a stranger in front of the house (someone unknown and therefore suspicious), but it could also be understood as “a foreigner” if that’s relevant in the story.

If you specifically mean stranger and want to avoid the “foreigner” reading, you can also say:

orang yang tidak dikenal = a person (who is) not known.

Why does it say di depan rumah instead of di depan rumah saya or di depan rumah tetangga saya?

Indonesian often leaves out possessives when they are obvious from context.

rumah here can be understood as “our house / the house in question in this story”.
The listener already knows we’re talking about my neighbor and the house area, so rumah is normally interpreted as the relevant house (very often the speaker’s or neighbor’s).

If you want to be explicit:

di depan rumah saya = in front of my house
di depan rumah tetangga saya = in front of my neighbor’s house

But in normal storytelling, di depan rumah is natural and sounds less heavy.

Where is the past tense in this sentence? How do we know it’s in the past?

Indonesian usually does not mark tense with verb endings (no equivalent to English -ed, will, etc.).

Past-ness is understood from:

Context (what you were talking about before/after).
Aspect words like:
- sudah (already)
- pernah (ever / has)
- tadi (earlier today)
- kemarin (yesterday)
- sempat (at one point / briefly did)

In your sentence:

sempat strongly suggests something already happened and is now over.
In a narrative, listeners automatically treat this as past:
→ My neighbor was once / briefly suspicious when he/she saw a stranger in front of the house.

So there is no special past-tense form; we infer it.

Is this sentence formal, informal, or neutral? Can I use it in everyday conversation?

The sentence is neutral and very natural.

Vocabulary: all standard words (tetangga, sempat, curiga, ketika, melihat, orang asing, di depan rumah).
Structure: standard, not slangy.

You can use it:

in casual conversation
in semi-formal contexts
in writing, like stories, essays, or reports

It’s not overly formal and not colloquial slang; it fits most situations.

Could I say Tetangga saya sempat mencurigai orang asing di depan rumah instead? How would that change the meaning?

Yes, you can. The difference is:

Original:

Tetangga saya sempat curiga ketika melihat orang asing di depan rumah.
→ Focus on the neighbor’s feeling/state: they were suspicious when they saw the person.

Alternative:

Tetangga saya sempat mencurigai orang asing di depan rumah.
→ Focus on the action of suspecting someone as an object.
Literally: My neighbor (briefly) suspected the stranger in front of the house.

Subtle nuance:

curiga: “He/She felt suspicious (in general, as a reaction).”
mencurigai: “He/She regarded that specific person as suspicious / suspected that person of something.”

Both are correct; the original is a bit more about the emotional reaction, the alternative more about direct suspicion toward that person.