Sometimes "de" is used with the plural (instead of "des") - please explain when this is so.
Thank you for using the Jiskha Homework Help Forum. This is all part of the "Partitive."
1. de + the definite article of the noun = some, any (du beurre / de la soie, etc.)
2. de, without the article, after a negative (Je n'ai pas fait de fautes. / Il n'a guère d'amis.)
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 (it is optional) (du bon cidre or de bon cidre = both correct)
5. also "combien de" and possessive are other uses of "de"
You are probably referring to #3. If not, please give examples you have seen.
Mme