The correct word for a in French depends upon the noun it follows. All nouns in French are either masculine, feminine or plural.
The articles un, une and des mean a or some and they have to agree with the gender of the noun.
These are called indefinite articles because you are talking about an unspecific thing or things. For example:
In the singular form (referring to one thing or person), use the articles:
|Singular masculine||Singular feminine|
|un vélo - a bike||une voiture - a car|
For plurals use des for all words and remember to make your noun plural too.
|Plural masculine||Plural feminine|
|des vélos - (some) bikes||des voitures - (some) cars|
When talking about jobs or professions in French, you don't need to use un/une before the job: