Learn Hardcore Indonesian: Jika kamu kehilangan kunci, ambillah kunci cadangan di resepsionis. - If you lose the key, take the spare key at the reception.

It’s common in written instructions and polite speech. In very casual contexts, people often just say ambil, or use ambil saja (“just take it”).

Is it okay to mix kamu with ambillah, or should I use Anda?

Mixing kamu (informal “you”) with ambillah (politer tone) is understandable but slightly mixed in register. More consistent options:

Informal: Jika kamu kehilangan kunci, ambil kunci cadangan di resepsionis.
Polite/formal: Jika Anda kehilangan kunci, ambillah kunci cadangan di resepsionis.
Neutral sign-style (no pronoun): Jika kehilangan kunci, ambillah kunci cadangan di resepsionis.

Could I replace jika with kalau or bila?

Yes:

Jika and bila are more formal.
Kalau is more colloquial.

All mean “if” and can head the clause:
Jika/Kalau/Bila kamu kehilangan kunci, …
They’re interchangeable here; choose based on desired formality.

Why kehilangan and not hilang? What’s the difference?

Hilang = “to be gone/lost” (state). Example: Kuncinya hilang. (“The key is missing.”)
Kehilangan (ke- -an) = “to lose (something),” typically unintentionally, focusing on the experiencer. Example: Saya kehilangan kunci. (“I lost my key.”)

Your sentence emphasizes the person losing the key, so kehilangan fits well.

Is di resepsionis correct? Should it be dari resepsionis or something else?

All are possible, with nuance:

di resepsionis = “at reception/with the receptionist” (location-focused; very common idiomatically).
di meja resepsionis / di bagian resepsionis = explicitly “at the reception desk/section.”
dari resepsionis = “from the receptionist” (source-focused).
Avoid ke resepsionis with ambil; use it only with a motion verb: Pergi ke resepsionis untuk mengambil kunci.

Why is it kunci cadangan and not cadangan kunci?

In Indonesian, modifiers usually follow the noun.

kunci cadangan = “spare key” (correct)
cadangan kunci would mean “a reserve of keys” or sound odd in this context.

Are there other common ways to say “spare key”?

Yes:

kunci serep (very common, informal–neutral)
kunci duplikat (duplicate key; implies a copy)
kunci cadangan (neutral–formal; good in signage)

Can I omit the subject and just say Jika kehilangan kunci, …?

Yes. Dropping kamu/Anda is natural in instructions and signs:

Jika kehilangan kunci, ambillah kunci cadangan di resepsionis.
The subject “you” is understood from context.

Would using silakan or tolong be more natural than -lah?

They’re all fine, with different shades:

Ambillah kunci cadangan … = polite imperative.
Silakan ambil kunci cadangan … = inviting/permission (“please go ahead and take…”).
Tolong ambil kunci cadangan … = requesting help (“please help by taking…”).

For signage, Silakan ambil… or Ambil kunci cadangan… are very common.

How should -lah be written? With a hyphen?

Write it attached, without a hyphen: ambillah (not “ambil-lah”).
Same rule for -kah and -tah: apakah, entahlah, etc.

Could I say kalau kuncinya hilang instead? Does it change the meaning?

Yes:

Kalau kuncinya hilang, … = “If the key is lost, …” (focus on the key’s state).
Kalau kamu kehilangan kunci, … = “If you lose the key, …” (focus on your experiencing the loss).

Both are acceptable; choose based on focus.

Does Indonesian mark tense here? Is it “lose” or “lost”?

Indonesian doesn’t mark tense on verbs. The conditional jika/kalau and context provide the time sense. The sentence can be read as “If you lose the key (at any time), take the spare key…,” which in English could be phrased with present or past depending on style (“lose” vs. “have lost”).

Is resepsionis the place or the person? What about resepsi?

Resepsionis = the receptionist (person). Idiomatically, di resepsionis means “at reception/with the receptionist.”
Resepsi = a reception event (e.g., a wedding reception), not the front desk.
For maximum clarity about place, use di meja resepsionis or di front desk (loan expression also used).

Shouldn’t it be “your key” (kuncimu/kunci Anda)?

Indonesian often omits possessive markers when context makes possession clear. Kunci here is naturally understood as “your key.” You can add possession if needed:

Informal: kuncimu
Polite: kunci Anda Example: Jika Anda kehilangan kunci Anda, … is grammatical but usually the second Anda is dropped as redundant.

How would I address multiple people?

Use kalian for plural “you” (informal):

Jika kalian kehilangan kunci, ambil kunci cadangan di resepsionis. In formal contexts, Anda can be singular or plural, so no change is needed:
Jika Anda kehilangan kunci, ambillah kunci cadangan di resepsionis.