Breakdown of To je luka iz koje plovimo na sjeverozapad.
biti
to be (sam, si, je)
to
that
na
on, at / to, onto (with motion) / about (thinking about)
iz
out of
Questions & Answers about To je luka iz koje plovimo na sjeverozapad.
Why is the relative pronoun koje in the genitive case here?
The case of a relative pronoun depends on its role in its own clause, not the main sentence. Here, it follows the preposition iz (out of/from), which always requires the genitive case. It takes the feminine singular form koje to agree in gender and number with luka (port).
Could we use od koje instead of iz koje to mean "from which"?
In this context, iz is the correct choice. You use iz when leaving a location that you would normally enter using the preposition u (into). Since ships sail into a port (u luku), they must sail out of it (iz luke). Using od would imply moving away from the general outside vicinity of the port, rather than out of the port itself.
Why do we use the preposition na for "to the northwest"?
Compass directions like north, south, east, and west almost always take the preposition na. Because the sentence describes motion toward a destination, na is paired with the accusative case. If you were just located in the northwest, you would still use na, but with the locative case (na sjeverozapadu).
If na takes the accusative here for motion, why does sjeverozapad look like a nominative noun?
It is indeed in the accusative case! Because sjeverozapad is a masculine inanimate noun (a non-living thing), its accusative form is exactly the same as its nominative form. This is an early rule that is easy to forget when you are looking for obvious case endings.