For saying ‘some’ or ‘any’
e.g. j’achete du pain (I am buying some bread)
You use de + the correct article …
de + le = du
de + la = de la
de + l’ = de l’
de + les = des
When playing an instrument we use jouer de (where de must agree with the article of the following noun), e.g.
e.g. je joue du piano
When talking about quantities, de doesn’t need a following article, e.g.
e.g. j’ai acheté un kilo de pommes
We use it for other common quantity expressions, which don’t need a following article, e.g.
e.g. beaucoup de peu de un peu de trop de assez de plus/moins de