Questions & Answers about U sobi je moja knjiga.
Why is it u sobi and not u sobu?
Because u can take different cases depending on meaning:
- u + locative = location, in / inside
- u + accusative = motion toward, into
Here the sentence describes where the book already is, so Serbian uses the locative:
- u sobi = in the room
- u sobu = into the room
So U sobi je moja knjiga means the book is already there, not moving there.
What case is sobi?
Sobi is locative singular.
The noun is soba = room, and for a feminine noun like this, the locative singular form is:
- soba → sobi
So:
- u sobi = in the room
This is a very common pattern with feminine nouns ending in -a.
Why is moja knjiga in that form?
Because moja knjiga is the subject of the sentence, and subjects are normally in the nominative case.
- knjiga = nominative singular
- moja matches it in