Futur Antérieur

Question 1

When to use the Future Perfect or Antérieur?

Answer 1

The French future perfect is most commonly used like the English future perfect: to describe an action that will have happened or will be finished by a specific point in the future.

J’aurai mangé à midi.
I will have eaten at noon.

Quand tu arriveras, il l’aura déjà fait.
When you arrive, he will already have done it.

Elle lui aura parlé demain.
She will have talked to him (by) tomorrow.

Dans un mois, nous serons partis.
In a month, we will have left.

There are three uses of the French future perfect that don’t correspond to the English future perfect:

1. In subordinate clauses that begin with the conjunctions aussitôt que, dès que, lorsque, quand, une fois que, and après que, the future perfect is used to express a future action which will be completed before the action in the main clause. In English, a present tense or past tense would be used here.Quand je serai descendu, tu pourras me le montrer.
   When I have come down, you can show it to me.Nous le ferons aussitôt qu’elle sera arrivée.
   We’ll do it as soon as she arrives / has arrived.
2. The future perfect can make simple assumptions regarding past events, where the English modal verb “must” would be used in conjunction with the past perfect:Pierre n’est pas ici ; il aura oublié.
   Pierre isn’t here; he must have forgotten.Luc est heureux ; il aura gagné.
   Luc is happy; he must have won.

Question 2

How do you conjugate it?

Answer 2

The French future perfect is a compound conjugation, which means it has two parts:

future of the auxiliary verb (either avoir or être) 
past participle of the main verb

Note: Like all French compound conjugations, the future perfect may be subject to grammatical agreement:

When the auxiliary verb is être, the past participle must agree with the subject 
When the auxiliary verb is avoir, the past participle may have to agree with its direct object

AIMER (auxiliary verb is avoir)
j'	aurai aimé	 	nous	aurons aimé
tu	auras aimé		vous	aurez aimé
il,
elle 	aura aimé		ils,
elles 	auront aimé

DEVENIR (être verb)
je serai devenu(e) nous serons devenu(e)s
tu seras devenu(e) vous serez devenu(e)(s)
il sera devenu ils seront devenus
elle sera devenue elles seront devenues

SE LAVER (pronominal verb)
je me serai lavé(e) nous nous serons lavé(e)s
tu te seras lavé(e) vous vous serez lavé(e)(s)
il se sera lavé ils se seront lavés
elle se sera lavée elles se seront lavées