Learn Hardcore Indonesian: Lorong sekolah itu panjang dan sejuk.

Indonesian doesn’t require a verb like “is” before adjectives. Adjectives can be predicates by themselves. So Lorong sekolah itu panjang dan sejuk is complete as “(That) school corridor is long and cool.” The linking word adalah is generally not used before adjectives; it’s used before noun phrases (e.g., Lorong sekolah itu adalah koridor utama).

What does itu mean here, and where does it go?

Itu marks definiteness or distance, roughly “that” (or often “the” when context makes something specific). In noun phrases it comes after the noun phrase it modifies:

lorong sekolah itu = that/the school corridor
With adjectives used attributively: lorong panjang itu or lorong yang panjang itu Use ini for “this”: lorong sekolah ini. In formal writing, tersebut can mean “the aforementioned.”

How does lorong sekolah work—does sekolah mean “school’s”?

Yes. Indonesian often forms “of/’s” relationships by putting two nouns together: lorong sekolah = the school corridor (corridor of a school). You don’t need an extra word like “of.” You can also use a prepositional phrasing if you prefer location: lorong di sekolah = corridor at the school.

Should I say Lorong di sekolah itu instead of Lorong sekolah itu?

Both are correct but slightly different in feel:

Lorong sekolah itu ties the corridor closely to that school (“that school’s corridor”). It sounds like a specific corridor you both know or can see.
Lorong di sekolah itu emphasizes location (“a/the corridor at that school”). It’s handy when you’re talking about one among many corridors there. To be clearly “one of the corridors at that school,” you can say Salah satu lorong di sekolah itu.

Are panjang and sejuk adjectives or verbs?

They are adjectives, but Indonesian adjectives can function like stative verbs when used as predicates. So panjang and sejuk here mean “is long” and “is cool” without needing a separate “is.”

How would I say “the long, cool school corridor” as a noun phrase?

Put the adjectives after the noun, optionally with yang for clarity:

lorong sekolah yang panjang dan sejuk
With definiteness: lorong sekolah yang panjang dan sejuk itu or lorong panjang dan sejuk itu Without yang can also be fine when short: lorong panjang dan sejuk itu.

Do I need dan between the two adjectives?

Yes—normally connect multiple adjectives with dan: panjang dan sejuk. In writing, a comma could sometimes separate descriptions, but dan is the default and most natural.

How do I make it plural?

Reduplicate the noun:

Lorong-lorong sekolah itu panjang dan sejuk = The corridors of that school are long and cool. You can also use quantifiers: Banyak lorong di sekolah itu panjang, Semua lorong di sekolah itu sejuk. Plural marking is often optional if context/quantifiers make plurality clear.

What’s the difference between sejuk, dingin, adem, and keren?

sejuk: pleasantly cool/refreshing (air, breeze, shade).
dingin: cold (lower temperature; can feel too cold).
adem: colloquial/informal for pleasantly cool (very common in speech).
keren: “cool” as in stylish/impressive, not temperature. So Lorong itu sejuk/adem = cool temperature; Lorong itu keren = it looks great/is impressive.

How can I say it “feels” cool?

Use terasa (feels) or talk about the air:

Lorong sekolah itu terasa sejuk.
Udara di lorong itu sejuk. Without terasa, sejuk already implies a state, so adding terasa highlights your perception.

Do I ever use adalah with adjectives like this?

No. Avoid adalah before adjectives: Lorong sekolah itu adalah panjang sounds wrong. Use adalah before noun phrases: Lorong sekolah itu adalah bagian terpanjang dari gedung. To emphasize truth with adjectives, use adverbs: memang, sungguh, benar-benar (e.g., Lorong itu memang panjang).

Do I need a word for “a” like sebuah?

Not here. Itu already makes it definite. Sebuah means “one (non-human item)” and is used when you need to specify a single, usually new/indefinite item:

Introducing: Ada sebuah lorong di sekolah itu…
As a subject, it’s possible but sounds odd if you’re just making a generic claim: Sebuah lorong di sekolah itu panjang… (better to be more specific or use context).

Are there synonyms for lorong, and how are they different?

lorong: corridor, passageway; also “alley” in some contexts.
koridor: corridor (more technical/formal; buildings, urban planning).
gang: narrow alley between houses/streets, not inside buildings. So inside a school building, lorong or koridor works; gang doesn’t.