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:
Example singular
an experiment:
plural (a suggestion)
flour
one flour
two flours?
happiness
one happiness
two happinesses?
wealth
one wealth
two wealths?
Coming back to the problem of the French partitive article in plural. There are sentences like the following:
Example
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.