"She does not have a sister."
Translation:У неё нет сестры.
What is the difference between "неё" and "её" anyway? Do we use "неё" if the sentence is negative?
Nope, it is easier than that.
Third person pronouns are он, она, оно, они (he, she, it, they).
In all of their oblique forms they use an initial Н aften all (almost all) simple prepositions:
- У неё нет кошки. = She does not have a cat.
- Я думаю о ней. = I think about her.
- Я думаю о нём. = I think about him.
Possessive её, его, их (her, his, their) are, quite obviously, derived from Genitive forms of она, он, они. However, they NEVER get an initial Н and do not change at all:
- У её брата нет кошки. = Her brother does not have a cat.
- Я думаю о её брате. = I think about her brother.
Does "oblique" mean "genitive when it's not being used as possessive"? I don't see н- forms or the word "oblique" in any pronoun charts I can find.
'Oblique case' (ко́свенный паде́ж) means 'any case except nominative'. (Nominative, on the other hand, is 'direct case', although this term is used much less often.)
This is related to the idea that all nouns are inherently nominative, while the others are somehow slanted.
What case does usually come after У and which one at the end? I can't understand so far which one to use when
I just read another Duolingo discussion that said this sentencr should use сестры becausr it is the genitive singular. However the audio pronounces it as сёстры, which is nom. pl. This is wrong right?
It should be «сестр́ы». If the audio has «сёстры», it's a bug.
This is not the neutral word order.
You could use «У неё сестры нет» to emphasise the word «нет», for example when someone claims that she has a sister and you refute the claim (therefore, «нет» sounds good emphasised because it's the most important word). However, in most contexts (i.e. when you don't have a reason for emphasis) this word order would sound strange.
Thank you for your answer. For me does not matter if this sentence would be accepted or not. It was just interesting for me to know if it is possible to use this word order.
To express possession, Russian typically uses "At X, there is an Y". Yep, the possessor is turned into "where". The possessed object is the grammatical subject of the sentence.
У requires the Genitive form of noun (or pronoun), so you have неё instead of она, него instead of он, меня instead of я and so on (in English, you also have a lot of roles where you just cannot put "she" instead of "her").
For statements of non-existence we use нет. The combination не есть has its uses in some particularly bookish contexts but it is not used in this meaning.