Conditionnel passé
Summary
The conditionnel passé is the French 'would have' form, used for unrealised past possibilities, regret and reproach, and formed with the present conditional of avoir or être plus the past participle.
Explanation
The conditionnel passé is a compound tense formed with the conditionnel présent of the auxiliary avoir or être + the past participle: j'aurais mangé, tu aurais mangé, il aurait mangé, nous aurions mangé, vous auriez mangé, ils auraient mangé; and with être, je serais parti(e), tu serais parti(e), il serait parti, nous serions parti(e)s, ils seraient partis. The auxiliary carries the conditional endings (-rais, -rais, -rait, -rions, -riez, -raient), and only the participle changes from verb to verb.
Choosing the auxiliary and agreeing the participle work exactly as in the passé composé. The usual verbs of movement and change of state take être (aller, venir, partir, arriver, naître, mourir…), as do all pronominal verbs (je me serais levé), and their participle agrees with the subject (elle serait partie). With avoir there is no agreement with the subject, but the participle agrees with a preceding direct object.
It is the French 'would have', expressing unrealised past possibilities, regret and reproach. Its chief use is the result clause of a past hypothesis whose si-clause is in the plus-que-parfait: Si j'avais su, je serais venu ('If I had known, I would have come'). It also conveys reproach or regret with devoir and pouvoir (Tu aurais dû me prévenir, 'You should have warned me'; J'aurais pu t'aider, 'I could have helped you') and reports unconfirmed news in journalism (L'accident aurait fait trois blessés, 'The accident reportedly injured three people').
The big pitfall is putting the conditional in the si-clause: *Si j'aurais su is wrong — the si-clause must take the plus-que-parfait (si j'avais su), and only the result clause takes the conditionnel passé. French never carries a conditional after si. Learners also forget participle agreement with être (elle serait partie, not parti).
Rule of thumb: conditionnel présent of the auxiliary + past participle = 'would have done'. It pairs with a si + plus-que-parfait clause (Si j'avais su, je serais venu), and 'si' itself never carries a conditional; choose the auxiliary and agree the participle exactly as in the passé composé.
Examples
Si j'avais su, je serais venu plus tôt. — If I had known, I would have come earlier. (Plus-que-parfait in the si-clause, conditionnel passé in the result clause.)
Tu aurais dû me prévenir. — You should have warned me. (aurais dû (devoir) expresses reproach or regret about the past.)
J'aurais aimé venir, mais j'étais malade. — I would have liked to come, but I was ill. (An unrealised past wish: the action did not actually happen.)
À ta place, je n'aurais rien dit. — If I were you, I would not have said anything. (À ta place implies an unstated past hypothesis; the result is the conditionnel passé.)
L'accident aurait fait trois blessés. — The accident reportedly injured three people. (Journalistic use: the conditionnel passé marks the news as unconfirmed.)
Common mistakes
Si j'aurais su, je serais venu plus tôt.
Si j'avais su, je serais venu plus tôt.
In a past hypothetical, the si-clause takes the PLUS-QUE-PARFAIT (si j'avais su), and only the result clause takes the conditionnel passé (je serais venu). French never puts a conditional after si, so *si j'aurais is a classic error. The pattern is: Si + plus-que-parfait, conditionnel passé.
Prerequisites
Related rules
moodcompound-tensehypothetical