That would be "a voi piace [...]", instead. " Vi" is an object pronoun. Check here, for example http://en.m.wikibooks.org/wiki/Italian/Pronouns#Object_Pronouns
"Vi" is the object. With "piacere" we have something strange. Instead of saying, "I, you etc like..." We say a thing is liked to me, you etc..."
So, "vi" is "to you" plural. Careful, we translate it like ordinary English. "You like fruit." (Not, "To you ....").
See here, thanks to Elheim
Perhaps a better English translation than "liked to me" would be "it is pleasing to me." If you think of piacere this way, it will help you remember the Italian sentence structure.
For example, take "I like coffee." Think "coffee is pleasing to me", and you will remember the proper construction in Italian.
Mi piace il caffè, o a me piace il caffè.
In Russian, we have the same indirect constuction:
"Вам (plural you, dative case, vi or a voi) нравятся (piacciono) фрукты (la frutta)", "Мне (first person pronoun, dative case, mi or a me) нравится (piace) пицца (pizza)".
In Ukrainian and Polish, however, there are two constructions, the first is like "I like something" in English, the second is like "Mi piace qualcosa" in Italian.
Ukrainian: "Я (I) полюбляю (like) їжу (food)", "Мені (a me) подобається (piace) їжа (cibo)".
Polish: "Ja (I) uwielbiam (like) jedzenie (food)"; "Mi (mi, a me) się podoba (piace) jedzenie (cibo)".
"Piacere" doesn't work the same way as "to like". Instead, it does as Spanish "gustar" (if you know any Spanish, this may sound familiar). "Vi piace la frutta" would be normally translated as "you like fruit", but in the Italian sentence "you" is not the subject. The original meaning is more like "fruit is likable to you"/"fruit pleases you"/etc.
Given this, we cannot use "tu" (which is a personal pronoun used only in place of the subject), but "ti" (for indirect object) or, in this case, "vi", because it's plural.
Duolingo percentage estimation of how much italian you know is just wrong.
Mathematically speaking, it rises too fast, and it stops in a place no one likes.
For example, just today in this lesson I learn the word "VI", that means YOU. It is very basic! How come I know 37%? And the two other languages I'm fluent (including native) it says I know around 50%.
I do not feel comfortable to share a link in "linkedin" saying I only know 50% of a language I have other international tests to prove I'm fluent! That is never going to happen. It would bad marketing for me, and as such, no marketing at all to duolingo!
You may not agree with me, and I respect your opinion. But if you do agree, I hope this message makes its way to the core's developers.
It should grown smoothly, slowly, and it should keep growing until more than 90%. Ok, if you want 10% or 15% to give only to those who helps translating texts, fine. Keep it growing until 85% at least.
For now I have 37% Italian, but I feel I know less than 15% of what I would know if compared to other languages. And Portuguese, for example, it says I know only 48% (an 11% difference!!) and I'm native, very well literate. I could say I know if not 100%, because you never know all, at least a 95%! And English, my second language, I know 58%, more than Portuguese? (Well, let me say, I just completed both trees in the same way, spending just 2 days each, making all tests. So it is not how I used duolingo.)
That is my humble opinion, that I hope more people share. Thank you for reading, and commenting. All opinions are valid and welcome. Have a nice day y'all. And of course, thanks duolingo for helping us to learn a language. I just hope it improves, that's all. I'm very grateful for this free wonderful tool.
How come "vi" which is basic would raise your fluency? This is a word that is very frequently used. When you speak, read and write, you can become fairly fluent without knowing every single word, but to become completely fluent you must know all the words.
Each course is different and do not have the same amount of vocabulary as each other. When you begin a course, you often learn words that are used more often than others and so your percentage rises faster then. When you get farther along in the course, it will take a lot more less frequently used words to raise your percentage just a little. The course does not pretend to include every word in a language and so the course does not give you 100% fluency, nor even close to 85%. You will have to finish increasing your vocabulary by reading, watching videos and movies and listening to music. Duolingo cannot properly test for your native language as it is testing what you know of one language as it was taught in Duolingo from another language. If you tested higher in "English from Portuguese" than you did in "Portuguese from English" that is really showing how well you translated from one to the other and not really how well you know the particular language. Check "Words" and I am ready to guess that more words were perhaps taught in one language than the other. A better test for a particular language would be a university test for the particular language from the country where that language is used. Fluency is just a gauge that helps us see how we might do with what we have learned so far and you must consider frequency of usage of the words. Each course does not necessarily teach the same words at the same time in the course either. You can increase your fluency. Spending 2 days is not enough to create the practice that gives Duolingo the confidence that you know words. Each word that you miss will lower your fluency!
Even if you know Portuguese, you are being tested on how well you know Portuguese from another language, so that your knowledge of the other language also changes your fluency score.
For example, I am extremely good in English and when I went to university, I only needed to take an essay class to complete all my English requirements because I tested so highly. On Duolingo I am learning languages backwards to English and my percentage is currently 8% English from Chinese. I wonder why? Hello! It is because I don't know Chinese. Yet this is higher than the 3% English from Japanese which I at least took a course in. This is because I spent more time practicing Chinese which I didn't know at all than Japanese.
I didn't even know there was a language proficiency rating in Duolingo in the first place, except for the possible initial evaluation to skip the first x lessons. I also wouldn't expect for something like a solid profiency rating to be expressed in a single number like a percentage value. (Yes, I'm aware of language standard ratings and tests in paricular for business, but still...) And I wouldn't expect too much in that respect from an app like Duolingo, where the courses' quality varies a lot. And I'd guess the percentage expresses something like the percentahe of accepted answers.
So, yes the rating may be off, but I would not use it for more as a crude estimate anyway.
I answered a similar question over 1 year ago, and you can find it elsewhere in this same thread, but: it's for the same reason "us" would replace "we" in an English sentence (I'm using "we" because it's not so apparent for "you").
"Voi" is a personal pronoun, used for the subject. Now, in English we would say: "you like fruit", "we like fruit", ... but while we translate "piacere" as "to like", because it's more natural in English, the actual meaning is something like "to please". So, what we're saying in Italian is something like: "fruit is pleasing to you", "fruit is pleasing to us". See? We need to use the (indirect) object pronouns.
And "piacere" has another quirk, which is the same with Spanish "gustar" or "agradar": the order of object and subject gets reversed. So, where in English you have a "subject-verb-object" (I like fruit), in Italian you have "object-verb-subject" (mi piace la frutta)
How do you say "Do you like the fruit?" Let's say your at the dinner table and their is a bowl of fruit that everybody has been periodically eating out of, oranges, grapes, apples, etc. How would you ask somebody, "Do you like the fruit?" Well, according to duolingo, it would not be "Vi piace la fruitta." You will get a red screen.