Learn Hardcore Indonesian: Kalau hujan deras, jalan tol itu sering banjir. - When it rains heavily, that toll road often floods.

kalau – very common in speech and informal writing; can mean if or when(ever) depending on context.
jika / apabila – more formal, often used in writing, instructions, official language.
ketika – usually means when (at the time that), not if. It’s used for definite times in the past or future, not for general conditions.

You can usually replace kalau with jika or apabila here with almost no change in meaning:

Jika hujan deras, jalan tol itu sering banjir.
Apabila hujan deras, jalan tol itu sering banjir.

Using ketika would sound more like you’re talking about a specific time, not a general tendency, so it’s less natural in this generic statement.

In kalau hujan deras, where is the subject “it” like in “if it rains heavily”?

Indonesian doesn’t need a dummy subject like English it for weather expressions.

hujan literally means rain / to rain.
hujan deras literally: heavy rain / raining heavily.

So kalau hujan deras is understood as if (there is) heavy rain or if it rains heavily.
Nothing is missing; Indonesian simply doesn’t say “it” in this kind of clause.

Why is it hujan deras and not deras hujan? What is the word order here?

Hujan (rain) is the main word, and deras (heavy, intense) is describing it.

hujan deras = heavy rain (noun + adjective) or to rain heavily (verb + manner).

The usual pattern is noun + adjective:

air panas – hot water
angin kencang – strong wind

Putting deras first (deras hujan) is not natural for this meaning. You sometimes see derasnya hujan, but that is a different structure meaning how heavy the rain is / the heaviness of the rain.

What exactly does jalan tol itu mean? Is itu “the”, “that”, or something else?

Jalan tol itu literally is that toll road, but it can also function as the toll road (a specific one, known from context).

jalan tol = toll road
itu = that / the (that one we know about)

Nuances:

jalan tol – could be general or non-specific (a toll road / toll roads in general).
jalan tol itu – specific: that particular toll road / the toll road (we both know which one).

So itu points to a specific, identifiable toll road.

Can I drop itu and just say kalau hujan deras, jalan tol sering banjir?

Yes, you can. The meaning changes slightly:

kalau hujan deras, jalan tol itu sering banjir
→ that specific toll road often floods when there’s heavy rain.
kalau hujan deras, jalan tol sering banjir
→ toll roads (in general) often flood when there’s heavy rain, or it’s less clear which toll road you mean.

Use itu when you mean a specific one that the listener is expected to recognize.

Does jalan tol itu refer to one toll road or several toll roads?

Indonesian nouns usually don’t mark plural, so jalan tol itu could be:

that toll road (singular), or
those toll roads (plural),

depending on context and what is logically possible.

If you want to force the plural, you can say:

jalan-jalan tol itu – those toll roads
semua jalan tol itu – all those toll roads

But in many real situations, context is enough and jalan tol itu is simply understood as one particular toll road.

Why is there no “to be” verb (like is/gets) before sering banjir?

Indonesian usually doesn’t use a separate “to be” verb before adjectives or many intransitive predicates.

Here, sering banjir is the predicate of jalan tol itu:

jalan tol itu – subject
sering – frequency: often
banjir – predicate (acts like a verb here: to flood / be flooded)

You don’t say jalan tol itu adalah sering banjir. That sounds wrong. Predicates like banjir, macet (jammed), rusak (damaged) come directly after the subject without a linking verb.

Is banjir a noun or a verb here? How can the same word be both?

Banjir is flexible:

As a noun: banjir = a flood / flooding
- Ada banjir di jalan tol itu. – There is a flood on that toll road.
As a verb-like predicate: banjir = to flood / be flooded
- Jalan tol itu banjir. – That toll road is flooded.

In jalan tol itu sering banjir, banjir functions as a verb-like predicate meaning floods / is flooded.

This flexibility is common in Indonesian; many words can be used as noun-like or verb-like without any change in form.

What is the nuance difference between sering banjir and sering kebanjiran?

Both can describe frequent flooding, but they feel slightly different:

sering banjir – neutral description:
- jalan tol itu sering banjir
  → that toll road often floods / is often flooded.
sering kebanjiran – kebanjiran has an affected/experiencing sense, often with a negative or slightly emphatic tone:
- jalan tol itu sering kebanjiran
  → that toll road often gets flooded (emphasis on being hit by floods).

In many contexts they’re interchangeable, but kebanjiran often feels more like “suffers flooding / gets flooded (again and again)”.

Could I say sering terjadi banjir di jalan tol itu instead? How does it differ from jalan tol itu sering banjir?

Yes, you can say:

Kalau hujan deras, sering terjadi banjir di jalan tol itu.

Differences in feel:

jalan tol itu sering banjir
- Simple, direct, very natural in speech.
- Focus: the toll road as a thing that often floods.
sering terjadi banjir di jalan tol itu
- Slightly more formal or descriptive.
- Literally: often a flood occurs on that toll road.
- Focus: the event of flooding happens often there.

Both are correct; the original sentence is more conversational.

Where can sering go in this sentence? Is jalan tol itu sering banjir the only correct word order?

The most natural position here is:

jalan tol itu sering banjir – subject + frequency adverb + predicate.

Other placements:

Sering, jalan tol itu banjir kalau hujan deras.
- Possible, but sounds like you’re emphasizing how often, and it’s more like a stylistic variation or spoken emphasis.
Jalan tol itu banjir sering – not natural in standard Indonesian.

So, for everyday speech, keep sering before the predicate:

subjek + sering + [predikat]

Should there be a word like menjadi (“become”) here, as in jalan tol itu sering menjadi banjir?

No. Jalan tol itu sering menjadi banjir is not natural.

Because banjir already works as the predicate (to flood / be flooded), adding menjadi (to become) is unnecessary and sounds wrong in this sentence structure.

You either say:

jalan tol itu sering banjir – that toll road often floods / is often flooded

or, if you really want menjadi with a noun phrase, you change the structure:

jalan tol itu sering menjadi tempat banjir.
→ that toll road often becomes a place where floods happen.

But for the original meaning, sering banjir is the correct and natural form.

Is the comma after kalau hujan deras required, and does it affect pronunciation?

In writing, the comma separates the conditional clause from the main clause:

Kalau hujan deras, jalan tol itu sering banjir.

You can also put the condition second:

Jalan tol itu sering banjir kalau hujan deras.

In speech, the comma corresponds to a short pause. Native speakers often pause slightly after kalau hujan deras if it comes first. Grammatically, both orders are correct; which one you use is mostly about emphasis and flow.