Breakdown of To mój bratanek, któremu kupiłem rower.
to
this
mój
my
kupić
to buy (perfective)
który
which, who (relative)
Questions & Answers about To mój bratanek, któremu kupiłem rower.
Why is the relative pronoun któremu used here instead of który or którego?
Któremu is the Dative case of który. We use the Dative here because the verb kupić (to buy) takes the Dative case for the person receiving the item (buying something for someone). Since the pronoun refers back to bratanek (a masculine singular noun), it takes the masculine singular Dative form.
Is bratanek the only word for nephew in Polish?
No, Polish uses different words depending on whose child it is! Bratanek specifically means a brother's son. If you were talking about a sister's son, you would use the word siostrzeniec.
Why doesn't the word rower change its ending, since it is the object being bought?
It actually is in the Accusative case, but you can't see a difference! Because rower is a masculine inanimate noun (a non-living object), its Accusative form looks exactly the same as its basic Nominative (dictionary) form.