Learn Hardcore Indonesian: Lampu jalan di depan sekolah sering mati ketika hujan deras. - The streetlight in front of the school often goes out when it rains heavily.

It’s a common noun phrase: [lampu] [jalan]. In writing it usually stays as two separate words, not lampu-jalan or lampujalan, although in very informal writing you might occasionally see it written together.

Is lampu jalan singular or plural here? How do we know?

Indonesian usually does not mark singular vs plural unless it needs to be emphasized, so lampu jalan here can mean:

the streetlight in front of the school, or
the streetlights in front of the school

Context decides. Because streetlights normally come in multiples and the sentence talks about a recurring situation (sering mati = often go off), many speakers will naturally understand it as the streetlights.

If you really want to emphasize plural, you could say:

lampu-lampu jalan (repeated noun, more formal/written)
banyak lampu jalan (many streetlights)

Why is there no word for the in lampu jalan di depan sekolah?

Indonesian does not have articles like a/an or the. Nouns stand on their own:

sekolah = school / the school / a school (depending on context)
lampu jalan = streetlight / a streetlight / the streetlight(s)

So lampu jalan di depan sekolah can be translated as:

the streetlight(s) in front of the school
streetlights in front of the school

The sense of the is understood from the situation, not from a specific word.

How does di depan sekolah work? Is depan a noun or a preposition?

The phrase breaks down as:

di = at / in / on (location preposition)
depan = front
sekolah = school

So di depan sekolah = in front of the school.

Here, depan behaves like a location noun (front) that is linked with sekolah:

literally: at the front (of) the school
functionally: in front of the school

This pattern is very common:

di belakang rumah = behind the house
di atas meja = on the table
di dalam mobil = inside the car

Could the order be di depan sekolah lampu jalan… instead of Lampu jalan di depan sekolah…?

Grammatically, you could say:

Di depan sekolah, lampu jalan sering mati ketika hujan deras.

But:

Lampu jalan di depan sekolah… sounds more natural as a neutral statement, because it starts with the topic (the lamps) and then adds where they are.
Starting with Di depan sekolah… shifts focus to the location first; it is often used when you are talking about that place and then describing what happens there.

So both are possible, but the original word order is the most usual and neutral.

Why is sering placed before mati? Can it come after the verb?

Sering is an adverb of frequency = often. In Indonesian, adverbs like sering, selalu, jarang most commonly come before the verb:

sering mati = often go off
selalu datang = always come
jarang hujan = it rarely rains

Putting sering after the verb (mati sering) would be unusual or sound wrong in this sentence. The natural pattern is:

subject + adverb of frequency + verb
Lampu jalan + sering + mati

Why is mati used for the light goes off? Doesn’t mati mean to die?

Yes, mati literally means to die, but in Indonesian it is also the normal word for to go off / to be off when talking about:

lights: lampu mati = the light is off / out
power: listrik mati = there’s a power outage
machines/devices stopping: mesin mati, HP mati

So:

Lampu jalan … sering mati =
The streetlight(s) in front of the school often go off / often stop working.

If something is permanently broken, you might also use:

rusak = broken, damaged
- Lampu jalan itu rusak. = That streetlight is broken.

Could we say sering rusak instead of sering mati? Would it sound the same?

You could say sering rusak, but the nuance is different:

sering mati = they often go off / go out.
It focuses on the light being off (maybe temporarily, maybe on and off).
sering rusak = they often break down.
It focuses more on defects or damage. It suggests they frequently need fixing.

In everyday speech about streetlights and electricity, mati is more common and sounds more natural for go off / out.

What is the difference between ketika, saat, waktu, and kalau for when? Why use ketika here?

All four can translate as when, but they have different feels:

ketika
- neutral, a bit formal/written
- often used for specific moments or conditions
- fits well in narratives and clear cause–effect statements
- ketika hujan deras = when it’s raining heavily
saat
- similar to ketika, slightly more conversational
- literally moment / time
- saat hujan deras = at the time of heavy rain / when it’s raining hard
waktu
- literally time
- very common in speech, slightly more casual
- waktu hujan deras = when it’s raining heavily (in spoken Indonesian)
kalau
- literally if, but also used as when in everyday speech
- especially for repeated, conditional situations
- kalau hujan deras = when it rains heavily / if it rains heavily

In this sentence, ketika hujan deras sounds neutral and clear: whenever there is heavy rain, they often go off. You could replace ketika with kalau in speech without changing the basic meaning:

Lampu jalan di depan sekolah sering mati kalau hujan deras.

What does hujan deras mean literally, and can I also say hujan lebat?

Breakdown:

hujan = rain
deras = heavy, pouring, with strong intensity (often about rain or flow)

So hujan deras = heavy rain / pouring rain.

You can also say:

hujan lebat = heavy rain

Deras and lebat overlap a lot here; both are natural. Hujan deras is extremely common in modern speech; hujan lebat may feel slightly more formal or descriptive, but both are fine.

Why is there no tense marker like do/does or -ed? How do we know the time of the action?

Indonesian verbs generally do not change form for tense. Time is understood from:

context
time expressions (e.g. kemarin, tadi, besok, sering, sudah)

In this sentence:

sering (often) implies a habitual / repeated action in general time (like English present simple).

So Lampu jalan di depan sekolah sering mati ketika hujan deras corresponds to:

The streetlight(s) in front of the school often go off when it rains heavily.

If you wanted to emphasize past, you could add something like dulu (in the past), but the verb mati itself would not change.

Is di in di depan always written separately, or can it be joined like didepan?

For location prepositions, di must be written separately:

di depan (correct)
didepan (spelling mistake)

General rule:

di + place = separate: di rumah, di Jakarta, di atas meja
di- as a passive prefix on verbs is attached: ditulis, dibaca

So in di depan sekolah, di is a preposition, so it stays separate.

Could I just say lampu di depan sekolah without jalan? Would it still mean streetlight?

If you say:

lampu di depan sekolah = the lamp(s) in front of the school

this is more general; it could be any lamp: a lamp over the gate, a decorative lamp, etc.

By saying:

lampu jalan di depan sekolah

you specify that you are talking about the streetlight(s) (the lamps that belong to the road/street). So jalan narrows the meaning and makes it clear that this is about public street lighting, not just any lamp near the school.