Genitive Case - Functions

Nouns use the genitive case:

when they indicate possession, or a relationship to another noun similar to that expressed by "of" in English
when they are the object of a genitive preposition
when they are the object of a verb which requires the genitive
when they are used in conjunction with certain special expressions
when they are used in expressions of indefinite time.

1) Was ist der Name des Politikers?
2) Während der Nacht bleibt es kühl.
3) Man bedarf oft der Ruhe.
4) Er ist dieses Themas kundig.
5) Wir sprechen eines Tages davon. What is the politician's name?
During the night it stays cool.
One often has need of rest.
He is expert in this topic.
We will talk about it some day.