Learn Hardcore Indonesian: Tolong bicara pelan di perpustakaan.

The sentence is an imperative: Tolong bicara pelan… = (Please) speak slowly…
The “you” is understood: [You] please speak slowly in the library.

You can add a pronoun if you want to be explicit:

Tolong kamu bicara pelan di perpustakaan. (casual, to someone your age or younger)
Tolong Anda bicara pelan di perpustakaan. (polite/formal “you”)
Tolong kalian bicara pelan di perpustakaan. (plural “you”, to a group)

But in real life, people usually just say Tolong bicara pelan… without stating “you”.

What exactly does tolong mean, and how is it used here?

Tolong literally means “help” (as a verb or interjection), but in front of another verb it works like “please”.

Two main uses:

As “help!” (urgent)
- Tolong! = Help!
- Tolong saya! = Help me!
As “please (do X)”
Structure: tolong + verb phrase
- Tolong bicara pelan. = Please speak slowly.
- Tolong tutup pintunya. = Please close the door.

In Tolong bicara pelan di perpustakaan, tolong softens the command and makes it polite, similar to English “please”, but with a slightly stronger “you are helping me by doing this” nuance.

Is bicara a verb? What’s the difference between bicara, berbicara, and ngomong?

Yes, bicara functions as a verb here: to speak / to talk.

bicara
- Meaning: to speak, to talk
- Common in everyday speech
- Can be used alone:
  - Saya mau bicara. = I want to speak.
  - Kita bicara nanti. = We’ll talk later.
berbicara
- Same basic meaning (to speak, to talk), but a bit more formal or bookish.
- Often used in writing, announcements, or more formal situations:
  - Beliau sedang berbicara. = He/She is speaking. (formal)
- In speech, bicara and berbicara are usually interchangeable, but berbicara may sound slightly more formal.
ngomong / ngomong-ngomong
- Very informal/colloquial: “talk, say”
- Used mainly in casual conversation:
  - Jangan ngomong keras-keras. = Don’t talk so loudly.
- You generally wouldn’t use ngomong in polite signs or in formal writing.

In your sentence, you could say:

Tolong berbicara pelan di perpustakaan. (correct, more formal)
Tolong bicara pelan di perpustakaan. (natural, neutral)

but not:

Tolong ngomong pelan di perpustakaan. (sounds too casual for a sign, okay in casual speech).

Why is it bicara pelan and not pelan bicara?

Indonesian usually puts adverbs after the verb they describe.

Pattern: verb + adverb

bicara pelan = speak slowly
jalan cepat = walk quickly
makan banyak = eat a lot

So:

bicara pelan = correct and natural
pelan bicara = sounds odd or unnatural in this context

If you want to emphasize how someone should speak, you can also use:

bicara dengan pelan (speak with slowness; more formal)
bicara pelan-pelan (speak very slowly / gently; more emphatic)

Is there a difference between pelan, pelan-pelan, and perlahan(-lahan)?

All of them relate to “slow / slowly”, but with slightly different flavors:

pelan
- Basic word for “slow / slowly”.
- Works as an adjective or adverb.
- Bicara pelan. = Speak slowly.
pelan-pelan
- Repetition often adds emphasis or a softer, more gradual feel.
- Sounds a bit more gentle, careful, or very slow.
- Bicara pelan-pelan. = Speak slowly / gently (really not fast, take your time).
perlahan / perlahan-lahan
- Slightly more formal / literary than pelan in many contexts.
- perlahan-lahan again emphasizes slowness.
- Bicara perlahan-lahan. = Speak slowly (carefully, gradually).

In your sentence, you could say:

Tolong bicara pelan di perpustakaan. (neutral)
Tolong bicara pelan-pelan di perpustakaan. (a bit more emphatic/softer)

What does di mean here, and how is it different from ke?

di is a preposition meaning “in / at / on” indicating location (where something is).

di perpustakaan = in/at the library

Contrast with ke, which indicates movement / direction (where you are going):

Saya di perpustakaan. = I am at the library. (location)
Saya ke perpustakaan. = I am going to the library. (movement)

In your sentence:

Tolong bicara pelan di perpustakaan.
= Please speak slowly in the library. (the place where you should speak slowly)

What is the structure of perpustakaan? How does it mean “library”?

Perpustakaan is formed from a root plus affixes:

Root: pustaka = a somewhat formal word meaning “book” / “writings”.
Affixes: per- … -an
This pair often creates a place related to the root.

So:

pustaka (book)
per + pustaka + an → perpustakaan = a place for books → library

This pattern appears in many words:

per + main + an → permainan = play → game
per + kara + an → perkara (slightly different, but same idea of forming nouns)

So perpustakaan literally is something like “the place of books”, which matches the idea of a library.

Is Tolong bicara pelan di perpustakaan polite enough for strangers, teachers, or older people?

Yes, the sentence is generally polite and acceptable in most contexts. Tolong already softens the command.

Politeness depends a lot on tone of voice and context, but grammatically:

For a sign / notice:
Tolong bicara pelan di perpustakaan. → fine, natural.
Speaking to a teacher/older person:
You might add an address term to be extra respectful:
- Tolong bicara pelan ya, Pak. (to a man)
- Tolong bicara pelan ya, Bu. (to a woman)
To be very formal (e.g., written notice):
- Mohon berbicara pelan di perpustakaan.
  (mohon is a more formal, slightly more distant “please”.)

So the base sentence is polite; you can adjust it with extra words if you need more or less formality.

Can I say Tolong berbicara pelan di perpustakaan instead? Is that more correct?

Yes, Tolong berbicara pelan di perpustakaan is also correct.

Differences in feel:

Tolong bicara pelan di perpustakaan.
- Very common in daily speech.
- Neutral, natural, slightly less formal.
Tolong berbicara pelan di perpustakaan.
- Slightly more formal / careful.
- Sounds good in announcements, written notices, or more formal speech.

Grammatically, both are fine. For casual everyday use, bicara is more frequent; for formal contexts, berbicara is also appropriate.

Can I move di perpustakaan to the front, like Di perpustakaan, tolong bicara pelan?

Yes, that word order is also correct.

Indonesian word order is flexible with location/time phrases. Both are acceptable:

Tolong bicara pelan di perpustakaan.
Di perpustakaan, tolong bicara pelan.

Putting di perpustakaan first just emphasizes the location a bit more, similar to English:

“In the library, please speak slowly.”

What you generally can’t do is split tolong far away from the verb in a strange way or move pelan to the front:

❌ Pelan tolong bicara di perpustakaan. (sounds unnatural)

Stick to:

Tolong bicara pelan di perpustakaan.
or
Di perpustakaan, tolong bicara pelan.