- "The giraffe is eating [some] leaves" - "Le girafe mange des feuilles"
- "The giraffe is eating the leaves" - "Le girafe mange les feuilles"
"les feuilles" can only be used as just "leaves" (and not "some leaves") when used with a verb of appreciation, aimer, détester, etc.
- "Le girafe aime les feuilles" - "The giraffe likes leaves"
- "Le girafe déteste les feuilles" - "The giraffe hates leaves"
Note how adding "some" would change the meaning of the last two sentences but doesn't change the meaning of the first sentence.
So just to check, does French grammar always use "des feuilles" for (just) "leaves" with verbs like manger as a rule, even when adding "some" would change the meaning in English? For example in English: "Although the giraffe (as a species) eats leaves, this newborn will feed on his mother's milk for four to six months before he begins eating leaves."
Yes, your sentence would use « des feuilles. »
However a generalization that started with “Leaves” would use “Les feuilles” as in “Leaves are the preferred food of Giraffes.”
So is manger a verb of appreciation that would mandate the use of "les feuilles)?
No, here “les feuilles” means “the leaves.” “Aimer” means “to like” and that would be a verb of appreciation.
Sorry, but I'm really confused. Isn't there a simple rule that tells you when to use feuilles; les feuilles or des feuilles?
Sorry, there are several rules. https://www.thoughtco.com/introduction-to-french-articles-1368810
I know what you are thinking of now. Generalizations in French also take the definite article.
Since we are talking about one particular giraffe, this is not a generalization.
If, however, we wanted to say “Giraffes eat leaves.”, then in French it would be “Les girafes mangent des feuilles.”
Except that I put the giraffe is eating leaves and was marked incorrect. Please explain that one.
It would be wrong. “des feuilles” would be “leaves”, but it would be possible to put “The giraffe is eating the leaves.” and that could be reported if not accepted as correct.
Oops I dictated that and it came out drafts. Of course I meant, the giraffe is eating leaves, should be accepted.
I understood that the definite article is sometimes used for a general noun, hence, les feuilles could be" the leaves" or the general "leaves" as opposed to some leaves "des feuilles"?????
No, if the sentence started with “Leaves are...” then the French would put “Les feuilles...”, but the verb “mange” uses “des feuilles” for “eats some leaves” in which we often just say “eats leaves.” The generalization would be about “giraffes” for “Giraffes eat leaves.”, but again when the definite article is used after a form of “manger” that wiuld be translated to the definite article in English.