- The noun/pronoun which the preposition modifies will always be in either the accusative, dative or genitive case.
- Prepositions are unchangeable. *
- Most prepositions are placed before the noun/pronoun they modify.
* "changes" can occur such as in prepositional contractions, however such prepositions are combined with definite articles to form one word rather than changed.
Learning prepositions may seem like entering a battlefield. True, prepositions are one of the trickier elements of German grammar, but once you've mastered the cases that go with each preposition, your battle is half won. The other half of the battle is knowing which preposition to use. For instance, the English preposition "to" can be translated into at least six different ways in German.
There are three prepositional cases: the accusative, the dative and the genitive. There is also a group of prepositions that can take on either the accusative or dative case, depending on the meaning of the sentence.
Commonly used prepositions such as durch, für, um always take on the accusative, whereas other common prepositions such as bei, mit, von, zu will always take the dative case.
On the other hand, prepositions in the dual-prepositions group (also called two-way prepositions) such as an, auf, in will take on the accusative case if they can answer the question whereto an action or object is going, whereas these same prepositions will take on the dative case, if they describe where the action is taking place.
Click on the following links to get more details and examples on each prepositional case.