Thank you! That was very helpful and much easier to read than some of these other websites. So, it is like the difference between much and many. You use 'di' when meaning some of a collective noun such as water or wine, but you use 'alcune' when meaning some of a countable noun, such as cookies or cats. Alcune is always used for plural. So if this is true, couldn't we say, "Alcune ragazze leggono alcuni libri," or vice versa?
Some girls read some books sounds like really poor English with at least a hint of misogyny. In most cases, an educated native English speaker would avoid using some twice in this sentence because it doesn't clearly convey enough information.
Doulingo lists the translation of alcune as: some, a few, no and the definition of dei as: of the, some, about the. I would say, in English, that it would make much more sense to either say: A few girls read some books., or Some girls read about the books.. Either option would make the English translation sound less repetitive and less like a five year old or misogynist is speaking. I don't know how faithful of a translation either would be though.
Based on Spanish's use of de (meaning: of, about, from), could this also possibly be translated as: Some girls read from the books.?
A great comment. There seems to be many Duo teaching-sentences that also teach or propagate on the under expectation or stereotypes of various groups. Females cop a lot of these here, plus innuendo. Social classes also. Why is 'Some girls read books' remarkable or used for teaching? Far better to use your sentence or other alternatives. Teachers can help give feedback to Duo I suppose.
We should remember that Duolingo is no more perfect than Google Translate. Both get it wrong at times. The literal translation could be 'some girls read of the books' A suitable meaning might be ' some girls read some of the books.' Google and another web translation service translate it as ''Some girls read books." Take your choice when speaking it - to avoid a loss of a heart on Duolingo write - "Some girls read some books."