When do I use du, de la, or des in French?

These are the partitive articles, used for an unspecified amount of an uncountable thing. Use 'du' before a masculine noun (du pain, du vin, du temps), 'de la' before a feminine noun (de la viande, de la patience, de la chance), and 'des' for the plural (des frites, des amis). Before a vowel or silent h, both 'du' and 'de la' collapse to 'de l'' (de l'eau, de l'huile, de l'argent).

Why does 'des amis' become 'd'amis' after a negative?

After a negative verb, indefinite and partitive articles collapse to plain 'de' (or 'd'' before a vowel). 'J'ai des amis' becomes 'je n'ai pas d'amis'; 'je mange du pain' becomes 'je ne mange pas de pain'. The same collapse happens after any quantity expression: beaucoup de pain (a lot of bread), un kilo de pommes (a kilo of apples), un verre d'eau (a glass of water). The article never reappears between 'de' and the noun in these constructions.

French Partitives and 'de'

The partitive is the article English speakers consistently miss. It marks an unspecified amount of something uncountable - food, drink, abstract qualities - and French requires it where English drops it.

The four partitive forms

Form	Used before	Example
du	masculine noun, consonant	du pain
de la	feminine noun, consonant	de la viande
de l'	any gender, vowel or silent h	de l'eau
des	plural, any gender	des frites

The same noun in different contexts gets different articles. Le pain (the bread) points to a specific loaf. Du pain (some bread) names an unspecified quantity. Un pain (a whole loaf) is one specific unit.

When to use the partitive

Any time you're talking about an unspecified amount of an uncountable thing.

Je mange du pain. (I eat / I am eating bread.)
Elle boit du cafe. (She drinks coffee.)
Il faut de la patience. (You need patience.)
Tu veux de l'eau? (Do you want some water?)
Nous avons des amis a Paris. (We have friends in Paris.)

Skipping the article - je mange pain - is always wrong. French requires either a definite article (le pain), an indefinite (un pain), or a partitive (du pain).

The negation rule: every article becomes 'de'

After a negative verb, indefinite and partitive articles collapse to plain de (or d' before a vowel). This is mandatory.

Affirmative	Negative
J'ai un chien.	Je n'ai pas de chien.
Je mange du pain.	Je ne mange pas de pain.
Elle a des amis.	Elle n'a pas d'amis.
Nous buvons de l'eau.	Nous ne buvons pas d'eau.

The definite article (le, la, les) does not change. It still points to a specific thing:

Je vois le chien. -> Je ne vois pas le chien.

The quantity rule: every article becomes 'de'

The same collapse happens after any expression of quantity. De sits alone between the quantity word and the noun; no article in between.

beaucoup de pain (a lot of bread)
peu de temps (little time)
assez d'argent (enough money)
trop de travail (too much work)
un kilo de pommes (a kilo of apples)
un verre d'eau (a glass of water)
une bouteille de vin (a bottle of wine)
un peu de patience (a little patience)

This is one of the cleanest rules in French: anywhere you'd say "of X" as a quantity, you say de X with no article.

The exception is la plupart (most), which keeps the article: la plupart des etudiants (most of the students), la plupart du temps (most of the time). Treat it as the odd one out.

d' before a vowel

De becomes d' before a vowel or silent h. This applies in both the negation and quantity constructions:

Je n'ai pas **d'**argent. (I don't have any money.)
beaucoup **d'**enfants (a lot of children)
un kilo **d'**oranges (a kilo of oranges)
pas **d'**eau (no water)

Partitive vs indefinite plural

The plural partitive des and the plural indefinite des look identical, and in most contexts they behave the same way. Don't lose sleep on the distinction.

Je mange des frites. (I'm eating chips - some chips, an unspecified plural.)
J'ai des amis. (I have friends - some friends, indefinite plural.)

Both behave the same way under negation (-> de) and quantity (-> de). For Foundation tier, treat them as one article.

Worked examples

Je voudrais du cafe et un croissant. (I'd like some coffee and a croissant.)
Il n'y a pas de pain dans le placard. (There's no bread in the cupboard.)
Elle boit beaucoup d'eau. (She drinks a lot of water.)
J'ai achete un kilo de pommes au marche. (I bought a kilo of apples at the market.)
Nous n'avons pas d'enfants. (We don't have any children.)
Donne-moi un peu de patience. (Give me a little patience.)

Common mistakes English speakers make

Dropping the partitive because English drops "some": writing je mange pain instead of je mange du pain. The article is mandatory. Keeping the article after a negative or quantity word: je n'ai pas du pain is wrong, it's je n'ai pas de pain; beaucoup du pain is wrong, it's beaucoup de pain. And confusing the negation rule with the definite article - je ne vois pas le chien stays le, because the article points to a specific dog you're not seeing.