I understand дверь is the singular for door, yet this appears plural, but its marked as incorrect.
It appears plural, but it's actually the singular genitive form of "Дверь".
But why is genitive used here? I thought genitive was for possession, negation and "some of something" instances. Is it the preposition?
Yes. A couple of prepositions take the genitive case, like "У". For each case there's at least a few prepositions that require it.
so how would you know the difference between plural "door" and genitive "door"?
Let's say it is the same sentence "Этот человек у двери" but it is plural. Then it will be "Этот человек у дверей".
Because у is something like near or by the door.. Should be в if someone stands in a door that's on the floor Someone corrects me if Im wrong
What you mean is usually said as "в дверях" (it sounds by the way as if there are two doors keeping the opening closed. Maybe it could have come from the upper class and something like a palace but I don't really know) and means that the door is open and the person you are talking about is in the opening.
"У двери" means that the door remains closed.
It's rather a big difference in case the mentioned person is unwanted.
Russian "у" seems to work like German "bei", except for which case it uses, if that helps anyone. (e.g., "Он у меня." = "Er ist bei mir." = "He is at my place.")
I think this is purely due to English and the fact that we can imply a word that should be there. Even though what you have written is understood, it is in actual fact grammatically wrong, as there is no verb (in this case to be). 'Is' is the verb that should be in the sentence.
What about answering the question "What person?". "That person by the door." In this case, the use of is would be incorrect. How to say that in Russian?
Not a native speaker of Russian, but I think the only problem with your suggestion is that this is punctuated as a complete sentence in Russian (just with the implicit "is"). I think that this would also be fine as your phrase, were the punctuation in accord with that.
Hm, maybe "этот человек у какой-то двери"(literally: this person is at some door)
Definiteness and undefiniteness is marked by "a/an" and "the" in English, but in Russian such things marked by word order in most cases.
I think they should both be accepted — just an oversight on Duolingo's part. I have reported.
Random speculation: дверь is one of the more common members of Russian's least common noun declension class. It shows up more than one might expect so that learners have a chance to realize that there is a third noun declension class.
человек (chelovek) sounds like chilaria to me
Can we please have human voice, because this isn't working?
Wait, I thought возле meant "near/by" ... would that still be acceptable in this sentence? And what is the real difference between возле and у anyway?
It does mean "on" and "at" indeed BUT such words are not always used exactly the same way in every language.
"На двери" sounds as if the door is on the ground and he is standing on it. Or as if he is hanging on it while it is still vertical. Sounds more like a Spiderman.
It sounds as if someone is somehow attached to the surface of it.
how about stands by the door?! duolingo marked it as a mistake... any ideas?!
It's usually Russian that uses standing/sitting/hanging verbs where English would just use "is," not vice versa.
"Near" should be accepted in place of "by". Literally the exact same meaning in English in this case
"There is someone at the door" seemed the most natural English translation to me, but it was marked wrong. Should it be accepted?
This sentence is about a "this person," i.e. you can at least point to them, as opposed to a wholly unidentified someone.
You actually ended up answering my question, I think.
So, my question was "why do we sometimes use это and sometimes этот for these similar sentences?" Thing is, это means "this is", while этот, on the other hand, just means "this".
So to answer your question, I believe the best choice would be это человек у двери, without т. But then I may be shamefully wrong, so if anyone would clear it up...
When does человек mean 'person' and when does it specifically mean 'man'? Or would I use мужчина for that?
I can see that the prepositional "у двери" also reads in english as "at the door" - there's an English-language expression that refers to a dire situation, which goes "the wolf is at the door" - i put that through Google Translate, and it came back, "волк у двери" just for general interest.
But we haven't been introduced to/presented with the info about "the genitive case" in this course yet, right? I've been trying to focus on one case at a time and researching as I go but will I have to look up and study all of the cases at once to do this course?
I read it as "by a door" instead of "by the door" - I guess I'm just not sure how to tell this with the context