"This is our book."
Translation:Это наша книга.
Prepositions have their own requirements, i.e. the same preposition will always use the same case (in the same meaning):
- у книги, около книги, из-за книги
- в книге = in the book, на книге = on the book
- в книгу = into the book, на книгу = onto the book
- под книгой = under the book
Cases depend on the role in the sentence, and on the structure:
- Книга сгорела. = The book burnt. (subject)
- У меня есть книга = I have a book (subject—at least, in Russian)
- Я хочу книгу. = I want a book. (direct object)
- Она ударила кошку книгой. = She slapped the cat with a book. ("cat" is a direct object, "book" is means of action)
Some structures trigger the Genitive. Genitive pf "possession" is VERY similar to "of" English. It uses the same word order and expresses a variety of meanings (not only the literal ownership):
- обложка книги = the cover of a book
- середина книги = the middle of the book
- качество книги = the quality of the book
The Genitive is also used for quantities (e.g., "a box of books", "three kilograms of rice") and negation of existence (in "нет книги").