"Beaucoup de" vs. "Beaucoup des"
This might be more of a question about "de" vs. "des," but I don't understand why this sentence was: "Un livre a beaucoup de pages" instead of: "Un liver a beaucoup des pages." Merci!
Actually, "beaucoup des" is used in the following situations [pasted from thoughtco.com]:
The only time beaucoup de and the other adverbs of quantity can be followed by a definite article is when they are referring to something specific, as in these examples:
J'ai acheté une chemise dont beaucoup des boutons s'étaient détachés I bought a shirt that a lot of the buttons had come off of (I'm talking about the specific buttons on this particular shirt)
Beaucoup des idées de Jean-Luc sont intéressantes A lot of Jean-Luc's ideas are interesting (I'm not referring to ideas in general, but rather the specific ideas that Jean-Luc has)
In most cases, if you can translate the French as "a lot of the" + noun or "a lot of ___'s" + noun, you use the definite article. Otherwise, if you only say "a lot of" + noun in English, just use de. (There are undoubtedly exceptions to this rule, but it should help you in most cases.)
I am afraid the second explanation so far is unclear as it reads that beaucoup des and beaucoup de are both used before specific instances. On another site beaucoup de is used before aspecific instances and so indeterminate articles and beaucoup des is used before determinate ones. Please refer to the explanation in the francaisfacile.com site. https://www.francaisfacile.com/exercices/exercice-francais-2/exercice-francais-92176.php