I was doing a Duolingo French dialogue exercise and came across the following sentence (last one):

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This would translate as "Oh no! The light has gone out", right? Why is éteindre here used with être? Wouldn't it be "La lumière s'a éteint"?

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    Does this answer your question? Rules of thumb for auxiliary verbs (avoir/être) in passé composé?
    – Maroon
    Commented Jan 22, 2020 at 15:24
  • @Maroon it has the same answer as the one I contributed, but the premise of the question seems to be about irregular verbs. If other posters feel it's a duplicate, I'm happy for it to be marked as such.
    – Nobilis
    Commented Jan 22, 2020 at 15:43
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    @Maroon It is difficult to say what's right here: the rule for the reflexive verbs is not at all a rule of thumb; it is a full-fledged rule.
    – LPH
    Commented Jan 22, 2020 at 17:02
  • @LPH: That post seems to have been used as the canonical post for "when to use être and when to use avoir as an auxiliary," hence why I linked it. But I agree that "rule of thumb" understates the rigidity of it, if you will.
    – Maroon
    Commented Jan 22, 2020 at 17:04
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    @Maroon That's it; the question is not well put and should have been modified. Such references do not make for clear information. It is then difficult to blame people that haven't been prepared to take that into account.
    – LPH
    Commented Jan 22, 2020 at 17:07

2 Answers 2


Éteindre exists in a reflexive and a none-reflexive form:

  • J’éteins la lumière: I switch the light off. Passé composé: J’ai éteint la lumière.
  • J’appuie sur le bouton: la lumière s’éteint: I press the button, the light goes off. Passé composé: J’ai appuyé sur le bouton: la lumière s’est éteinte.

So the form to use with the passé composé dépends on what you mean to say. And the reflexive form requires être (more infos here)


All reflexive verbs use être in passé composé.

So in the case of éteindre, if you put the light out, you'd say:

Tu a éteint la lumière.

But when the same sentence is reconstructed reflexively, use être instead of avoir:

La lumière s'est éteinte (note also the gender being marked).

This is a nice summary of when to use avoir vs être and covers the case above.

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    That is the reason, it is just a matter of rule; it's one of those rules you have to know by heart. (The auxiliary verb for all compound tenses is always "être" for the reflexive verbs.)
    – LPH
    Commented Jan 22, 2020 at 13:46

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