In English, prepositions, such as to, for, with and against, are followed by their objects. In the prepositional phrase, "to the train station," "train station" is the object of the preposition "to."

Each German preposition calls for a specific case for its object. Most common prepositions take either dative or accusative.

The Preposition "zu" and its Contractions

The preposition zu takes the dative and means "to" (a certain place). The contraction for zu dem is zum. Dem is the dative singular form for the definite article in masculine and neuter:
 

The contraction for zu and der is zur. Der is the dative singular form for the definite article in feminine:
 

The Preposition "an" and its Contractions

The preposition an takes the dative to describe the position of something at or on the side of something. The contraction for an and dem is am.
 

Before feminine singular nouns, its form is not contracted.
 

Examples of zu and an

• Entschuldigen Sie, wie komme ich zum Parkhotel?
• Wie komme ich zur S-Bahn?
• Bitte, bleiben Sie am Apparat.