Questions & Answers about Oružje je u stanu.
Stanu is in the locative singular.
After u when it means in / inside / at a place, Croatian normally uses the locative case to show location:
- u stanu = in the apartment
- u kući = in the house
- u školi = at school / in the school
The basic dictionary form is stan. In the locative singular, it becomes stanu.
A very useful contrast is:
- u stanu = in the apartment → location
- u stan = into the apartment → movement/direction
So in Oružje je u stanu, the meaning is static location, so u stanu is correct.