The Partitive

In English, we might say "I want coffee". However, in French you need to indicate the quantity, if you know it, or conversely indicate that you do not know the exact quantity. In French, one would say the equivalent of "I want some coffee". To render the meaning of the word "some" in this case, we use what is called the partitive.

The partitive is form by taking 'de' and the definite article, i.e. du, de la or de l'.

Examples

Je veux du café.                          I want (some) coffee.
[How much coffee? Some. No specific amount. Not one cup. Not 20 grams of coffee. Just some.]

J'ai acheté des fleurs.                  I bought (some) flowers.
[How many flowers did I buy? I did not stipulate. I just bought some or other unknown quanity.]

Je voudrais une bouteille d'eau.  I want a bottle of water.
[Here I am being specific. I want a bottle, that is one bottle, of water, hence we cannot use de l'.]

Je voudrais de l'eau.                    I want (some) water.
[How much water? I did not say. Therefore, the partitive is required.]

J'ai trois amis.                             I have three friends.
[I am being specific about how many friends I have and therefore cannot use the partitive.]

J'ai des amis.                               I have (some) friends.
[How many friends do I have? You do not know. I did not tell you. Thus I used the partitive.]