Last week we explored some of the most common usages of the French preposition de. In addition to a preposition that can express possession, relation, and direction, or to link verbs, de can be used to express quantity, either alone or as part of an expression of quantity. Once again, the rules governing how de changes depends on its usage—and this can be quite tricky.

De means something like “some” and is often used in French to express an indeterminate quantity of something. Unlike in English, if you are not giving a specific amount of something (two kilos of bananas, for example) you need to use this preposition. So, where in English, you would say “I ate bananas for breakfast today,” in French you would need to say something like “I ate some bananas for breakfast today” (J’ai mangé des bananes pour le petit déjeuner aujourd’hui.).

Just as de can change when it acts as a directional, relational, or possessional preposition depending on the noun that follows it, so can it change when expressing quantities. This means:

When de precedes a masculine noun, it becomes du.

When de precedes a feminine noun, it becomes de la.

When de precedes a noun that begins with a vowel, it becomes de l’.

Easy enough, right? Not so fast! This gets trickier when de becomes part of an expression of quantity (or if de refers to something “unspecific”—more on this later).

If de is part of an expression of quantity, it actually acts as an adverb (or an adverbial expression). The reason why this is tricky is because these expressions can be difficult to recognize. Let’s take a look.

Here is a list of common adverbial expressions with de:

assez de (enough of)

beaucoup de (a lot of)

un peu de (a little of)

une douzaine de (a dozen of)

un kilo de (a kilogram of)

une bouteille de (a bottle of)

With any of these adverbial expressions, de DOES NOT CHANGE based on the gender of the noun that follows. In fact, de does not change at all—except when it precedes a noun that starts with a vowel. Then, it becomes d’.

Let’s take a closer look.

Je veux avoir une bouteille de rouge, s’il vous plaît. (I’d like to have a bottle of red, please.)

Notice how de stays the same here and does not change into du. This is because it is part of an expression of quantity, une bouteille de.

Check back next week for the final part of the series on tricky prepositions (and adverbial expressions!).