French
How to get natural French 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
| Language tags | fr-FR, fr-CA, fr-BE, fr-CH |
| Script and direction | Latin script, left to right |
| Token use | Measure with token counting on your own text; non-Latin scripts and long compounds usually take more tokens per sentence than English. |
Register and form of address
Choose tu or vous explicitly. Vous is the default for brands and support; tu suits casual consumer products. Mixing them in one conversation is a common and very visible slip.
Numbers, dates and currency
Decimal comma (12,50 €) and a space before the currency symbol in France; a non-breaking space before : ; ? ! and inside « guillemets ». Dates: 5 novembre 2026, or 05/11/2026.
Common pitfalls
- Canadian French differs in vocabulary (courriel, magasiner) and often in formality; use
fr-CAfor Québec audiences. - Gender-inclusive writing (le point médian: client·e·s) is contested; state your house style.
- Anglicisms in tech copy: say whether “e-mail” or “courriel”, “cloud” or “nuage” is preferred.
A system prompt line that works
Writing the language instruction in French itself is a strong signal:
Réponds en français, en vouvoyant l'utilisateur, avec un ton professionnel et chaleureux.(Answer in French, addressing the user as vous, with a professional and warm tone.)
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
- Collect 30 or more real French messages, including short, misspelt and mixed-language ones.
- Have a fluent speaker grade replies for correctness, register and naturalness; then calibrate a rubric grader on their grades (Evaluate).
- Check rendering in your actual UI: line breaks, truncation and fonts.
- Re-run the set whenever you change the prompt or the model.