Genitive case: When to use it?
In German there are four cases: nominative, accusative, dative and genitive.
Nouns (and related words) are declined – that means they change their form according to the case. The four cases indicate the role that the noun/noun phrase has in the sentence.
The genitive case is mainly used:
1. to express possession
Das ist das Haus meines Vaters.
In modern German the genitive is mainly used in written formal language. In spoken informal language phrases with the preposition von are used rather than the genitive. (das Zimmer von meinem Bruder instead of das Zimmer meines Bruders).
2. always after the following prepositions: während, wegen, statt, trotz, ….
Wegen des Regens kommen wir nicht.