We need the cases in German to indicate a certain function of a noun in a sentence. We do this by adding endings to the articles or adjectives that come before a noun (In some cases also to the noun itself).
In a sentence, nouns appear in one of the four cases, depending on their role: nominative for the subject, accusative for the direct object, dative for the indirect object, and genitive to show possession.
Nominative Case (der Nominativ)
The subject of a sentence is always in the nominative case. As a rule, the subject is the person or thing performing the action of the verb.
E.g. Der Junge isst die Wurst. (The boy eats the sausage.)
The boy is the subject of the sentence: He is the one eating the sausage.
Accusative Case (der Akkusativ)
The direct object of a sentence is always in the accusative case. The direct object is the person or thing directly affected by the action of the verb.
E.g. Der Junge isst die Wurst.
The sausage is the direct object. It‘s the thing that is being eaten.
Dative Case (der Dativ)
The indirect object of the sentence is always in the dative case. Think of the indirect object as the person or thing that receives the direct object.
E.g. Der Junge gibt dem Hund die Wurst. (The boy gives the sausage to the dog.)
Here, the dog is the indirect object because the boy gives the sausage to it.
The sausage is the direct object, the thing that‘s being given, and the boy is the subject, as he is doing the action, he gives. If a sentence has two objects, one of them is probably an indirect object. If in doubt, try
translating the sentence into English: If you can put ‚to‘ before one of the nouns, that‘s the
indirect object in the German sentence.
Genitive Case (der Genitiv)
The genitive case is used to indicate possession. The person or thing that possesses is the genitive case.
E.g. Der Hund des Jungen frisst die Wurst. (The boy‘s dog eats the sausage.)
The boy possesses the dog, so he is in the genitive case.
Cases matter - die vier Fälle sind wichtig
The German cases are crucial to understand if you want to communicate properly in German, because the definite and indefinite articles may change spelling, depending on which case they appear in.