Third conditional (si + plus-que-parfait)

To talk about how a past event could have ended differently, use the third conditional.

Like in English, it combines an "if" clause (the condition) with a main clause (the imagined result):

  • si
    • plus-que-parfait (if someone had done something)
  • conditionnel passé (they would have done something else)
If the lawyer had prepared the file, he would not have lost the trial.
Si l'avocat avait préparé le dossier, il n'aurait pas perdu le procès.
If she had testified, the jury would have acquitted the suspect.
Si elle avait témoigné, le jury aurait acquitté le suspect.

When si is followed by il or ils, it contracts to s'il or s'ils.

If they had convicted him, the sentence would have been terrible.
S'ils l'avaient condamné, la peine aurait été terrible.

Reversing the Clauses

You can also place the result before the condition. When the sentence starts with the result, drop the comma.

They would have acquitted him if the witness had spoken.
Ils l'auraient acquitté si le témoin avait parlé.
He would have testified if the jury had been more patient.
Il aurait témoigné si le jury avait été plus patient.