We have seen that de + definite article (in singular) is a partitive article. The logic consequence would be that also the definite article in plural would function as a partitive article.
First let us think about a question: Tthe partitive article determines an undefined quantity of things that are not countable. If things are not countable, how to have a plural of something that cannot be counted? Even if it sounds absurd, please follow the following experiment:
plural (a suggestion)
Coming back to the problem of the French partitive article in plural. There are sentences like the following:
Je vois des hommes.
I see people.
Je veux des pommes.
I want apples.
But in these cases des (de + les) is no partitive article as per definition, but it functions as such. Therefore, we regard des (despite the slight imperfection) as a partitive article, because this will help us to know when to use them, as you will see now.