Indefinite Articles — Les articles indéfinis
Indefinite articles in French are equivalent to 'a', 'an', or 'some' in English. They are used before nouns to indicate a non-specific person or thing. They also agree in gender and number with the noun.
Rules
Un — used before masculine singular nouns (un garçon = a boy)
Une — used before feminine singular nouns (une fille = a girl)
Des — used before plural nouns (des livres = some books)
In negative sentences, un/une/des become de or d' (Je n'ai pas de chat = I don't have a cat)
Examples
J'ai un frère et une sœur. — I have a brother and a sister.
Il y a une pomme sur la table. — There is an apple on the table.
Elle a des amis à Paris. — She has some friends in Paris.
Je n'ai pas de voiture. — I don't have a car.
C'est un bon professeur. — He is a good teacher.
Nous avons des devoirs à faire. — We have some homework to do.