"Do you know her book?"
Translation:Вы знаете её книгу?
Yes, it's accusative.
When unsure, you can use this tool to show all the forms of the noun: http://starling.rinet.ru/cgi-bin/morphque.cgi?flags=endnnnn
Can the pronoun be left out in Russian, like in Spanish or Italian:
Yo tengo un gato = Tengo un gato
Io ho i piatti = Ho i piatti
No. In Spanish, the pronoun is usually not used; in Russian, it's usually used.
You can drop it in colloquial speech, but this course teaches you standard Russian, and you don't usually drop pronouns in standard Russian.
It's wrong brcause «ты» is only used with «знаешь», «вы» is only used with «знаете».
Some languages might allow mixing such forms (e.g. Portuguese normally uses 'tu conheces', or 'você conhece', but in colloquial speech you can use 'tu conhece'), but not Russian.
When you are being formal, you address the person as if there are several people. You might be speaking to just one person, but their opinion is so valuable as several people’s opinion.
So, you are using the plural form («вы» is originally plural). The verb forms are different for singular and plural forms.
This is not unlike older English:
- ‘thou knowst’ = ты знаешь (singular, less polite),
- ‘you know’ = вы знаете (plural or polite).
- you can’t say ‘*you knowst’ = *вы знаешь (wrong!).
(The difference between Russian and English is that in English, you could actually say ‘thou know‘ instead of ‘thou knowst’. In Russian, you can’t say *ты знаете (this is wrong).
In English, when ‘thou’ was falling into disuse, people no longer followed the rules related to it, so ‘thou know’ became a possible alternative for ‘thou knowst’. But the Russian, «ты» is still alive and well, and so are the rules requiring to use separate verb forms with it.)
It's definitely correct. It's probably some Duolingo's bug. You can report it using the report button next time you get this sentence.
I've reported that my answers should have been accepted for at least 3-4 times over the course of 3 weeks and yet they are still not accepted.
Ты знаешь её книгу?
Знаешь её книгу?
The word order is unnatural. When the object is not a pronoun, we usually place the object after the verb.
Swapping verb and object here, like you've done, emphasises either «её книгу» or «знаешь» людей. This could work in some contexts, for example, for contrast:
— Ты её знаешь? 'Do you know her?' (1)
— Впервы́е ви́жу. '[I] am seeing her for the first time.'
— Не в лицо́. Ты её книгу зна́ешь? 'Not her face. Do you know her book?' (2)
(1) «Её» is a pronoun, so this is not an inverted word order; pronouns usually come before the verb.
(2) «Её кни́гу» is a phrase, so it's normally placed after the verb. Placing it before the verb creates an inverted word order to emphasise «её книгу».
Here, we contrast 'knowing her face' (literally: knowing her in face, i.e. by face/by sight) and 'knowing her book'. 'Her book' is contrasted with previous statement, so we place it first to show it's the important word. However, in most other contexts, «Ты её кни́гу зна́ешь» would sound very unnatural.
[РУС] «Свою» значит 'принадлежащую подлежащему предложения'. Здесь подлежащим является «Вы», поэтому «Вы знаете свою книгу?» значило бы «Вы знаете Вашу книгу?». Такой вопрос можно задать, если вы подозреваете, что книгу за автора писали литературные рабы, а автор сам её толком не знает. Однако такой вариант не принимается, так как он не соответствует английскому.
[АНГ] «Свою́» means 'belonging to the grammatical subject of the sentence'. Here, «Вы» 'you' is the subject of the sentence, so «Вы зна́ете свою́ кни́гу?» would mean 'Do you know your book?'. You could ask his question if you thing the book might had been ghost-written and the author doesn’t really know it. However, it’s not accepted here because it doesn’t match the English translation.
Thank you for the clarification. Not easy for me to get used to that. Practice practice.