What are the German cases, and when do I use them?

There are four cases in the German language: nominative, accusative, dative, and genitive. There are different rules on when to use each specific case.Nominative: The nominative case is used for the subject of a sentence, e.g. Der Mann kauft einen Hut.Accusative : The accusative case is used for the direct object of a sentence - Der Mann kauft einen Hut. The accusative case also denotes movement - Ich gehe ins (in das) Kino. It is also used as a rule after certain prepositions - bis, durch, entlang, für, gegen, ohne & um.Dative: The dative case is used for the indirect object of a sentence - the person to or for whom something is done, e.g. Ich gebe dem Mann einen Hut (I give a hat to the man). The dative also denotes a lack of movement - Ich bin im (in dem) Kino. It must always be used after the prepositions aus, außer, bei, mit, nach, seit, von & zu, as well as after certain verbs (helfen, danken, gefallen...)Genitive: The genitive case denotes possession - Der Hut des Mannes (of the man). It can also be replaced with the dative von dem Mann.