There are three forms of the French indefinite article. Articles agree in gender and number with the noun they determine.
un masculine une feminine des m or f plural
The indefinite article refers to an unspecified person or thing.
Ex. J’ai un livre. – I have got a book. => J’ai des livres. – I have got books.
C’est une fille. – This is a girl. => Ce sont des filles. -These are girls.
When referring to a person’s profession, the indefinite is not used in French.
Ex. Il est acteur. – He is an actor.
Elle est chanteuse. – She is a singer.
Some practice exercises for ESL teachers and students.