French Si Clauses: If-Sentences in Three Patterns

« If I had known… » French builds every if-sentence from just three patterns — and one golden rule that instantly removes the most common mistake. Here are the si clauses, sorted from everyday to regretful.

The three patterns

The golden rule

French children learn it as a rhyme: « Les si n’aiment pas les -rais » — si never sits next to a future or conditional. English says “if I WOULD have known”; French forbids it: the conditional lives in the OTHER half of the sentence. Si + imparfait, conditional after the comma. Every time.

Two bonus uses of si

• Suggestions: Si on + imparfait = “how about…”: Si on allait au cinéma ? (Shall we go to the movies?)
• The other si: answering a NEGATIVE question with yes: « Tu ne viens pas ? » — « Si ! » (Yes I am!). Oui can’t do this job.

Small spelling note

Si elides only before il(s): s’il pleut, s’ils veulent — but si elle, si on, si Anne. Writing « si il » is the typo French teachers circle in red.

FAQ

Can si + présent be followed by the future?

Yes — the future goes in the RESULT half: S’il fait beau demain, on ira à la plage. What’s banned is future/conditional directly after si.

What tense is « si j’avais su »?

Plus-que-parfait (had known) — pattern 3, the regret machine. Pair it with the conditionnel passé: je ne serais pas venu. The past tenses are unpacked in the past tenses guide.

Is « si j’aurais » ever right?

Never in standard French — it’s the classic error even natives joke about. Si j’avais, je donnerais. Let the rhyme protect you: les si n’aiment pas les -rais.

Drill the result half on the conditional chart and conditionnel passé chart; the full tense system is in the verb tenses guide.

Quick practice

Keep going: The two tenses doing the heavy lifting here each have their own lesson: the conditional and the plus-que-parfait.