Indonesian

How to get natural Indonesian out of Syntic models, and what to check before you ship. The general rules for every language are on Work in other languages.

At a glance

Register and form of address

Formal Bahasa Indonesia uses Anda for “you”; casual consumer apps often use kamu. Jakarta slang (gue/lo) is too informal for most products.

Numbers, dates and currency

Decimal comma and dot for thousands (Rp1.250.000). Dates: 5 November 2026 or 05/11/2026.

Common pitfalls

• Indonesian has no grammatical tense; time words (sudah, akan, sedang) carry it. Check that time-sensitive replies (“your refund has been sent”) are unambiguous.
• Many loanwords have official forms (unduh for download, surel for email) but English terms are common; state a preference.
• Malay (ms) is close but not the same; do not use one for the other.

A system prompt line that works

Writing the language instruction in Indonesian itself is a strong signal:

Jawablah dalam Bahasa Indonesia yang sopan dan jelas, gunakan sapaan "Anda".

(Answer in polite, clear Indonesian, addressing the user as Anda.)

Keep the rest of your instructions in whichever language your team maintains best; the model follows mixed-language system prompts reliably, and the reply language follows this line.

Test before launch

1. Collect 30 or more real Indonesian messages, including short, misspelt and mixed-language ones.
2. Have a fluent speaker grade replies for correctness, register and naturalness; then calibrate a rubric grader on their grades (Evaluate).
3. Check rendering in your actual UI: line breaks, truncation and fonts.
4. Re-run the set whenever you change the prompt or the model.