Parts of Speech: Adverbs & Prepositions by Elvin

Most German prepositions take an object in only one particular case. For instance, mit (with) always takes the dative case, as in mit dem Geld (with the money), while durch (through) always takes the accusative case, as in durch den Wald (through the forest). The two-way prepositions take an object in either the accusative or dative case — but they don't do so just at random. When an accusative/dative preposition answers the question "where to?" (wohin?), it takes the accusative case. When answering the question "where" (wo?), a two-way preposition takes the dative case.