les déterminants: les articles indéfinis

Forms

In French, few nouns can stand alone. Most need to be introduced or 'determined' by an article. As in English, an article is characterized as either definite ('the') or indefinite ('a', 'an'). 

In French, articles are also masculine or feminine, and  singular or plural, according to the gender and number of the noun they determine. Here are the indefinite articles in French:

masculine singular: un

feminine singular: une

plural: des

In the examples above, note the difference in pronunciation of un  and des before words beginning with a consonant (un chien, des chiens) and before a word beginning with a vowel sound (un étudiant, des étudiants). These are examples of liaison.

uses

As the English 'a' 'an' or 'some', the indefinite articles un, une, des refer to nouns which are non-specific. Un or une may also indicate quantity, 'a' or 'an' in the sense of 'one.' Contrast the use of the indefinite and definite articles in the first two sentences below. 

The indefinite plural des is always necessary in French, but its English equivalent 'some' is often omitted.

'de' after the negative

In a negative sentence, the indefinite articles un, une, des are replaced by de or d':

NOTE: Following the verb être, the indefinite articles un, une, des remain unchanged in the negative:

before a plural adjective

Before a plural adjective which precedes a noun, des usually becomes de. If the adjective comes after the noun, des does not change to de.

with adjectives of profession, nationality, and religion

Professions, nationalities and religions are considered adjectives in French and need no article after the verbs être and devenir.