Nominative 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 nominative case is mainly used:

1. for the subject of the sentence

Der Mann arbeitet.

Die Frau wohnt in Berlin.

2. with the following verbs:  sein, werden, bleiben, heißen

Der Mann ist ein Freund.

Herr Schmitt wird der Direktor.

USEFUL TO KNOW!

Unlike in English where the subject of the sentence is usually in front of the verb, in German the subject can be found either in front or after the conjugated verb. The nominative helps to identify the subject. 

Der Mann ist heute im Büro.

Heute ist der Mann im Büro.