In short, "My guitar on the desk" doesn't have a verb, and context should tell you if you're emphasizing on the guitar(Noun) or Where(Place) the guitar is.<pre>
For (an elaborate) example, if you owned a guitar shop, and someone asked,"Which is your favorite guitar?" You may say, "My guitar on the desk" because you are specifying a particular guitar. In the same shop, if you were asked, "Where is your favorite guitar?" You could reply,"My guitar IS on the desk." because this time you are specifying the location of the guitar.</pre>
In Russian, the context of what has happened in the past, makes whatever you are trying to say make sense. There is no need to complicate the sentence, by directing your attention to which guitar it is or where the guitar is. The prior knowledge already tells you.
I hope that made sense :) Keep in mind that I'm still learning as well. Feel free to point out anything I messed up on, we're all just learning :D
The O does not have a long o sound, but it does have a short o sound as in the word "not". The accent is on the E. https://www.duolingo.com/comment/8256103 http://forvo.com/search/%d0%a1%d0%a2%d0%9e%d0%9b%d0%95/
Duo's programming is not so sophisticated. It might be frustrating, but keep in mind that it's just a program, not a real person judging your answers in real time. So it can't make a decision like "oh, that's obviously a typo, because a native English speaker couldn't make such a mistake, so I'll let it slide". Usually if a typo leads to another real word, Duo marks it as a mistake. It can't do anything more complicated than that.
Interesting that you should ask that. In Norwegian, Swedish and Danish "chair" is "stol" which probably sounds quite similar and in Dutch it is only slightly different "stoel". The Russian "стул" probably sounds closer to the English word "stool" which has a slightly different meaning being something to sit on but which has nothing to support your back. It is like a game of telephone where one person says a word to someone else and as it is passed on it changes slightly here and there.
I suppose that "over" ≈ "поверх". Well, if you put on a shirt and than you put on a coat, can you say something like "I've put a coat over the shirt"? In Russian we say "Я надел пальто поверх рубашки".
"На" is more similar to English "on": "я стою на полу" = "I stand on the floor". If you say something like "I stand over the floor", I will think that you are levitating :)
We use the word стол for both table and desk. Even for the top surface of kitchen counter. Well, we have special word for school desk - пАрта, but it usually means the special kind of desk, whats surface isn't parallel to the floor (I've seen such desks only in my pre-school class and in old Soviet films. Btw sloping surface is pretty comfortable for writing! It's a bit like easel, but not so vertical). When the desk's surface is parallel to the floor, we don't call it парта, we can call it пИсьменный стол (writing table) or рабОчий стол (working table). Sometimes we have to use additional words, for example, there are two tables in my kitchen: one is countertop and another is dinner table, so I often have to use the defining word: "обЕденный стол" (dining table) or "кУхонный стол" (literally "kitchen table", usually that means only the countertop). But if there is only one type of tables in the room, we just call it стол.
I'm referring to the nouns they reference as prepositions. The instructions at the beginning of this lesson say "use на in front of open spaces or events to mean "at or on", whereas it says use "в before buildings and places with boundaries" to mean "at or in". It appears that advice is bad in this case.
Russian nouns have gender (M/F/N). Words describing a noun reflect the gender. Masculine nouns (стол) most often end in a consenant and don't change their descriptive words (not the technical term but you understand) so "my table" would be мой стол. Feminine nouns most often end in "a" and add an "a" to the ends of their description word; Моя вода, моя кошка, моя гитара...
@Integer2 - Потому, что "на" значит именно "on", за некоторыми исключениями (например, ""на почте" переводится как ""in the post office; на кухне - in the kitchen; на Аляске - in Alaska. Но это объясняется тем, что эти места в давнем прошлом находились под открытым небом. Не знаю точно об Аляске честно говоря >).
В данном предложении, чтобы выразить смысл что гитара "in the table", надо употреблять предлог "в".