Learn Hardcore Indonesian: Terowongan itu sempit, jadi mobil harus berada di lajur kanan. - That tunnel is narrow, so the car must be in the right lane.

In Indonesian, demonstratives come after the noun. terowongan itu means “that tunnel” or “the tunnel (in context).” Putting itu before the noun (e.g., itu terowongan) would normally be read as “That is a tunnel,” with itu acting as a pronoun, not as a determiner.

Can I omit itu? What changes if I do?

If you drop itu, Terowongan sempit is likely read as “narrow tunnel” (a noun phrase), not a full sentence. To keep the meaning and sentence structure, either keep itu, use -nya to mark definiteness (Terowongannya sempit), or restructure the clause:

Karena terowongan sempit, mobil harus berada di lajur kanan. In conversation, people might omit itu when the context is crystal clear, but the version with itu is clearer and more standard.

What does jadi do here, and how is it different from jadi meaning “to become”?

Here jadi is a coordinating conjunction meaning “so/therefore,” introducing a result. As a verb, jadi means “to become” (e.g., Dia jadi guru = “He becomes a teacher”). In your sentence, it’s clearly the conjunction because it links two clauses (cause → result).

Could I use karena, sehingga, or maka instead of jadi?

Yes, with slight stylistic differences:

Karena terowongan itu sempit, mobil harus berada di lajur kanan. (Because…)
Terowongan itu sempit sehingga mobil harus berada di lajur kanan. (…so that/as a result)
Terowongan itu sempit, maka mobil harus berada di lajur kanan. (formal tone)
Terowongan itu sempit, jadi mobil harus berada di lajur kanan. (neutral, conversational)

Why use berada di instead of just di?

berada di explicitly states “to be (located) in/at,” and sounds a bit more careful or formal. Using only di with harus (Mobil harus di lajur kanan) is common in speech and understood, but many speakers prefer harus berada di in careful writing.

What’s the difference between berada di and ada di?

Both can indicate presence at a location. ada di emphasizes existence/presence (“to be there”), while berada di emphasizes being positioned/located there and feels more formal. In practice:

Mobil harus ada di lajur kanan = the cars must be present in the right lane.
Mobil harus berada di lajur kanan = the cars must be located/positioned in the right lane. Both are acceptable here.

Should it be ke lajur kanan instead of di lajur kanan if movement is implied?

Use:

di lajur kanan for location/state (“in the right lane”).
ke lajur kanan for movement (“to the right lane”). If you want to express moving, say:
Mobil harus pindah ke lajur kanan.
Mobil harus masuk ke lajur kanan.
Mobil harus ambil lajur kanan.

Is lajur the same as jalur?

Not exactly, though many people mix them:

lajur = a lane on a road (most correct in traffic-lane contexts).
jalur = a route/track/path (e.g., jalur sepeda, jalur pendakian). It’s often used colloquially for lanes, but lajur is the precise term for car lanes.

Does mobil mean “car” or “cars”? How do I make it plural?

Indonesian doesn’t mark plural by default. mobil can mean “car” or “cars,” depending on context. To make it explicitly plural, you can use:

Reduplication: mobil-mobil
Quantifiers: semua mobil, banyak mobil, beberapa mobil Avoid para; it’s used only for people.

Could I use kendaraan instead of mobil?

Yes, but kendaraan means “vehicle(s)” (broader: cars, motorcycles, trucks, etc.). Use mobil if you specifically mean cars; kendaraan if the rule applies to all vehicles.

Why di lajur kanan and not di sebelah kanan?

di lajur kanan = “in the right lane” (specific, traffic term).
di sebelah kanan = “on the right side (of something)” (spatial, not necessarily a lane). You might say di sebelah kanan jalan (on the right side of the road) when not referring to marked lanes.

Is the comma before jadi correct?

Yes. You’re separating two independent clauses, and placing a comma before jadi is standard in this use. Alternatives are a semicolon or rephrasing with karena/sehingga.

What’s the nuance of sempit compared with kecil?

sempit = narrow/cramped (focus on width or tight space).
kecil = small (overall size). A tunnel can be large but still sempit if the passage is narrow.

Is terowongan the same as lorong?

No:

terowongan = tunnel (typically through a hill, under a river, etc.).
lorong = corridor/hallway/passage inside a building or between rooms.

Any spacing rule I should know about di here?

Yes. di as a preposition is written separately: di lajur. The prefix di- (passive voice) is attached to verbs (e.g., dikerjakan). Never write dilajur when you mean “in the lane.”

How strong is harus? Could I use wajib, perlu, or sebaiknya instead?

Strength of obligation, strongest to softest:

wajib = obligatory/mandatory (often legal or formal).
harus = must/have to (strong necessity).
perlu = need to/necessary (softer).
sebaiknya = should/it’s advisable (recommendation). Choose based on how strict the requirement is.

Can I flip the order and start with the reason clause?

Yes:

Karena terowongan itu sempit, mobil harus berada di lajur kanan. You can also use sehingga:
Terowongan itu sempit sehingga mobil harus berada di lajur kanan.

Any pronunciation tips for key words?

terowongan: te-ro-WO-ngan (ng as in “sing”).
jadi: JA-dee (j like English “jam”).
lajur: LA-joor (j like “jam”).
kanan: KA-nan (both a’s like the a in “father,” but shorter).