Dative: To Whom?

The dative answers komu? (to whom?). It marks the person who receives something or is helped. Use it after dát, koupit, poslat, zavolat, psát, pomáhat, děkovat, věřit, rozumět, and after k/ke (towards).

• Masculine animate nouns take -ovi (or -u): bratrovi, tatínkovi. Names almost always take -ovi: Petrovi, Karlovi.
• Feminine nouns in -a take -e/-ě, and the consonant before it can change: -ka → -ce, -ra → -ře, -ha → -ze: mamince, sestře, Evě, Tereze.
• Masculine and neuter things after k/ke take -u: ke stolu, k oknu (but k řece).
• The words in front change too: ten → tomu, ta → té, pan → panu: tomu pánovi, té paní, panu Novákovi.

In Czech, zavolat takes the dative: Zavolám mamince. (I'll call mum.)