kuzyn

In a sentence

• Mój kuzyn mieszka w Krakowie.

  My cousin lives in Kraków.

  Here, 'kuzyn' refers to the speaker's male cousin, and the sentence identifies his place of residence.

• Czy spotkałaś się z moim kuzynem?

  Have you met my cousin?

  In this question, 'kuzynem' is the instrumental case of 'kuzyn', used because of the verb 'spotkać się' (to meet).

• Rozmawiałem z kuzynem o wakacjach.

  I talked to my cousin about the holidays.

  Here, 'kuzynem' is again in the instrumental case, following the verb 'rozmawiać' (to talk).