"You are eating black grapes."
Translation:Tu manges du raisin noir.
In French, we use the collective "du raisin" which refers to the nature of the fruit, not to its actual physical appearance. Here, we are dealing with "an undefined quantity of" raisin. It works like the English "fruit" which is collective, while in French, it is not.
When the French refer to the grapes, they say, for ex: "vous mangez des grappes de raisin"
I just recently listen to a youtube video by Luis. He stated that at this point, Duolingo is able to give the reason a wrong answer is given about 15% of the time. The video was about a year old. I notice if I make too many mistakes, it may be able to correct me on one of my mistakes, but not multiple mistakes.
I don't have more information, although I thank northernguy for his explanation of how computer based systems work. I am impressed with the model of duolingo, which is "kill two birds with one stone". Lots of people like or need to learn a second language. Lots of information is out there on the web in only one language. How can that information be translated into more languages? By people learning languages and practicing their skills of understanding on translating articles. And it's something at this point in time computers are mediocre at doing. But millions of humans, working together are quite good at it.
That is the way a computer based system works. If you use a singular article with a plural noun, very often there is no possible way for the computer to know which one was correct because it depends on what you were trying to say. If you make a typo that changes the word into another legitimate word that conflicts with something else in the sentence, it is impossible for the computer to know that you entered a typo and that is what the problem is. It may identify your typo as the problem or it may present the other word as the issue. But it does identify something, marks you incorrect and expects the student to go to comments pages to find out what is going on if he is confused.
It looks through the text, finds something that is inconsistent, identifies it to the user and stops.
Generally, "de" means "of", while "du" means "of the" or "some", being a contraction of "de le", which is never used. However, when it is negative, or there is an adjective in front of the noun, "de" is used instead of "du", e.g. "pas de raisin" "de bon raisin noir." Perhaps this is the cause of your confusion?
Most American varieties have "slip skins," or skins that slip easily off the berries, while those from Europe often have skins that are securely fastened to the fruit. Colorwise, grapes fall into either the "white" or "black" category. "White" grapes actually range in color from pale yellow-green to light green, while "black" grapes range from light red to an extremely deep purple. We'll call them by their more common names, green and red. "Black" grapes aren't necessarily black. ;)
"Le raisin et le vin" was translated in another question as, "Grapes and wine". On this question I hesitated about putting" "du", because of that last question. I still don't have an understanding of the "du" "le" thing. I've found some of the "explanations" on discussions quite confusing and contradictory. Any help from a native speaker would be greatly appreciated.
"du, de la or de l' " express the meaning of "some" in front of a singular, uncountable noun.
I eat (some) bread = je mange du pain = an undefined quantity of a mass thing
- "du" is used in front of masculine singular nouns starting with a consonant
- "de la" is used in front of feminine singular nouns starting with a consonant
- "de l' " is used in front of singular nouns starting with a vowel or a non aspirate H