Learn Hardcore Indonesian: Bantal kecil berguna ketika kami beristirahat di hutan pada malam hari. - A small pillow is useful when we rest in the forest at night.

Indonesian does not have definite or indefinite articles (no a, an, the). Nouns on their own can be definite or indefinite depending on context. If you want to emphasize “a small pillow,” you can add sebuah (e.g. sebuah bantal kecil), but it’s not obligatory.

Why is the adjective kecil placed after the noun bantal, instead of before like in English (“small pillow”)?

In Indonesian, the default order is noun + adjective. So you say bantal kecil, rumah besar, tas merah, etc. Placing the adjective first would sound unusual.

What part of speech is berguna, and how is it formed?

Berguna is a stative verb (or predicative adjective) meaning “to be useful.” It is formed from the root guna (“use”) with the prefix ber-, which often turns nouns or roots into verbs indicating possession of that quality:
– guna (use, usefulness) → berguna (is useful)

Why does the sentence use ketika kami beristirahat, and could I use saat instead of ketika?

Both ketika and saat mean “when.”

ketika is slightly more formal/literary.
saat is more colloquial but equally correct.
So you could say saat kami beristirahat di hutan pada malam hari without changing the meaning.

Why is kami used here instead of kita?

Both mean “we,” but:

kami is exclusive (excludes the listener).
kita is inclusive (includes the listener).
Use kami when you’re talking about your group and not including the person you’re speaking to.

Why is it di hutan and pada malam hari? Couldn’t I say pada hutan or di malam hari?

– di marks place: di hutan (“in/at the forest”). You cannot use pada for a place in this case.
– pada often marks general time points: pada malam hari (“at night”).
However, di malam hari is also common in spoken Indonesian and perfectly acceptable to mean “at night.”

Why do we say malam hari instead of just malam?

malam alone is “night,” but in time expressions you often add hari to emphasize the time period: di malam hari. Dropping hari isn’t grammatically wrong, but adding hari is more natural in many contexts.

Why is there a prefix ber- in beristirahat? Can I just say istirahat?

Both beristirahat and istirahat can function as verbs meaning “to rest.”

beristirahat is the more “official” verb form.
istirahat is also used colloquially as a verb or noun (“rest”).
In practice, you’ll hear both, and neither is wrong here.

Could I start the sentence with the time clause, like Ketika kami beristirahat di hutan pada malam hari, bantal kecil berguna?

Yes. Indonesian allows flexible word order for time/place adverbials. Placing ketika… at the front emphasizes the time first. Both versions are correct.