The grammatical function of a noun, pronoun, or adjective in a sentence.

German has four cases: nominative (subject), accusative (direct object), dative (indirect object), and genitive (possession).

Examples

Nominative:
Der Mann schläft.
The man is sleeping.

Accusative:
Ich sehe den Mann.
I see the man.

Dative:
Ich gebe dem Mann das Buch.
I give the book to the man.

Genitive:
Das ist das Buch des Mannes.
That is the man's book.

See also

Declension
Inflected adjective Nominative
Accusative
Dative
Genitive