Question

I forgot, what's the difference between de and du? how do you know which one to use?

Answer 1

With the partitive:
1. de + definite article of the noun = du, de la, de l', des
2. de, withot the article after a negative: poas de fautes (for example)
3. de, without the article, when an adjective precedes a plural noun = de vieux souliers / de longues rues
4. de, with or without the article, when an adjective precedes a singular noun (you will see both: du bon cidre OR de bon cidre

With adverbs of quantity, use "de" without the article before a noun
examples: assez de liveres, beaucoup de filles, combien de garçons

With nouns of quantity, use "de" without the article beofre another noun.
examples: une boite de bonbons
une bouteille de lait
une douzaine d'oeufs

With nouns of material (something made of...), use "de" without th e article
examples: une pièce d'or, une voiture de bois

With possession or relationship, use "de" instead of 's or s'
examples: les livres de Paul, le bureau du professeur, la grand-mère des enfants, le mari de l'actrice

Without giving me examples of what you are doing, you will see it is difficult to tell you which you want!

Sra (aka Mme)