Learn Hardcore Indonesian: Dia berbicara sopan kepada tetangga kami.

dia is gender-neutral and can mean either he or she. Indonesian pronouns do not mark gender.
If you really need to specify, add a descriptor or rely on context: dia laki-laki (male), dia perempuan (female), or use a name/title.
For a respectful third person, use beliau (he/she, honorific).

What’s the difference between berbicara, bicara, berkata, mengatakan, ngomong, and ngobrol?

berbicara (kepada/dengan …): to speak/talk; neutral/standard. Example: Dia berbicara sopan kepada tetangga kami.
bicara: shorter, everyday form of berbicara. Example: Dia bicara sopan…
berkata (kepada … + clause/quote): to say (often followed by what was said). Example: Dia berkata kepada tetangga kami bahwa…
mengatakan (sesuatu kepada …): to say/tell (transitive). Example: Dia mengatakan hal itu kepada tetangga kami.
ngomong (sama/ke …): colloquial to say/speak. Example: Dia ngomong sama tetangga kami.
ngobrol (dengan …): to chat (two-way, casual). Example: Dia ngobrol dengan tetangga kami.

Why is sopan after the verb? Is it an adverb? Can I say dengan sopan?

Indonesian often uses adjectives as adverbs. sopan functions adverbially here (politely).
Both berbicara sopan and berbicara dengan sopan are correct. dengan sopan can feel a bit more explicit/formal.
Do not use sopan-sopan for this meaning.

Why use kepada here? How is it different from dengan, ke, pada, or sama?

kepada: to (a person). Best choice for speaking to someone. Example: berbicara kepada tetangga.
dengan: with (someone), implies interaction. Example: berbicara dengan tetangga (talk with).
ke: to (a place/direction). Not standard with berbicara; in casual speech people say ngomong ke, but avoid berbicara ke in formal usage.
pada: at/on/with; sometimes used as to, especially with things or in formal writing. For people, kepada is the safer pick.
sama: very colloquial for to/with. Example: ngomong sama tetangga.

Is tetangga singular or plural here? How do I say neighbors?

tetangga kami can mean our neighbor or our neighbors; Indonesian doesn’t mark plural by default.
To make it clearly plural:
- para tetangga kami (formal)
- tetangga-tetangga kami (reduplication)
- semua tetangga kami or tetangga kami semua

Why kami and not kita? What’s the difference?

kami = we/us (excluding the listener).
kita = we/us (including the listener).
tetangga kami means our neighbor(s), not necessarily the listener’s. tetangga kita implies the neighbor(s) that you and the listener share.

Can I use ia instead of dia? What about beliau?

ia can replace dia as a subject and sounds more literary/formal: Ia berbicara…
ia is not used after prepositions; you’d use kepadanya (to him/her), not kepada ia.
beliau is a respectful third-person pronoun for elders/superiors: Beliau berbicara…

How do I show past, present, or future time in this sentence?

Indonesian verbs don’t inflect for tense. Add time/aspect words:

Past: Tadi dia berbicara…, Dia sudah/telah berbicara…
Ongoing: Dia sedang berbicara…
Future: Dia akan berbicara…, Nanti dia berbicara… Context or time expressions like kemarin (yesterday), besok (tomorrow) also help.

Can I move sopan or the prepositional phrase around?

Yes, with slight changes in emphasis:

Dia berbicara dengan sopan kepada tetangga kami.
Dia berbicara kepada tetangga kami dengan sopan.
Kepada tetangga kami, dia berbicara dengan sopan. (fronting for emphasis; common in writing) Avoid placing sopan before the verb in this sentence.

Is it okay to drop the subject dia?

In casual conversation, subjects are often omitted if clear from context: Berbicara sopan kepada tetangga kami could be understood.
In careful or written Indonesian, keep dia to avoid ambiguity.

Pronunciation tips for the tricky words?

Is berbicara ke acceptable?

Standard: berbicara kepada/pada someone.
berbicara ke is nonstandard in formal contexts. In casual speech you’ll hear ngomong ke or bilang ke, but with berbicara, use kepada/pada.

How would I say talk with our neighbor (emphasizing two-way conversation)?

Use dengan:

How would I say this with a name or a respectful title?

Replace the noun phrase:

Dia berbicara sopan kepada Pak Budi. (Mr./Sir)
Dia berbicara sopan kepada Bu Sari. (Mrs./Ma’am) Common titles: Pak (adult man), Bu (adult woman), Mas/Mbak (young man/woman, Javanese-influenced), context-dependent.

Are there synonyms or related words for sopan?

sopan = polite, well-mannered.
Near-synonyms: santun (polite/courteous, a bit more formal), ramah (friendly, not exactly polite), halus (refined/gentle, context-dependent).
Negatives: tidak sopan (impolite), kurang sopan (not very polite).

How do I say he always/usually speaks politely to our neighbor(s)?