Être is the verbe auxiliaire in the following instances:
a. When one of the following 16 verbs are used:
for example:
Napoléon est né en Corse.
Napolean was born in Corsica.
Corrine et Luc sont allés en France.
Corrine and Luc went to France.
There is no logical reason for these 16 verbs taking être as the verbe
auxiliaire. You just have to remember them. Many people use this mnemonic:
the first letter of each verb spells out DR/MRS VANDERTRAMP.
b. When the verb is reflexive, for example:
Georges s’est couché à minuit.
Georges went to bed at midnight.
Paulette et Guy se sont baignés hier.
Paulette and Guy went swimming
yesterday.
c. Unlike with the verbe auxiliaire avoir, when être is the verbe auxiliaire, it
must agree with the subject. If the subject is:
masculine singular—add nothing
masculine plural—add ‘-s’
feminine singular—add ‘-e’
feminine plural—add ‘-es’
for example:
Paulette est allée au café.
Paulette went to the café.
Paul et Luc sont allés au café.
Paul and Luc went to the café.
Paulette et Pauline sont allées au café.
Paulette and Pauline went to the café.
3. Negative Sentences
When a sentence in the passé composé is negative, the ne…pas (ne…jamais,
etc.) go on either side of the verbe auxiliaire, for example:
Je n’ai pas vu le monstre.
I didn’t see the monster.
Nous ne sommes pas allés au cinéma.
We didn’t go to the movies.
Elle n’a jamais bu d’alcool.