Case By Case
As beginning students of German quickly become aware of, the German language features many “cases", each and every single one having its own unique headaches. In German, certain prepositions take certain cases. When one says “to take the case of", it means that the following noun object (and any associated articles and adjectives) will be declined in that case.
Be careful not to mix up independent prepositions with in/separable verbs with preposition prefixes. There is a fine line between the two structurally, but one that can mean something completely different if you stray on the wrong side.
For the most part, German preposition usage follows the same word order as in English; it is noted in this article where this is otherwise.
Bear in mind that these translations are only approximate: while following these translations will get you more-or-less understood, there are a few finer points of meaning that can be missed. The same English preposition may take on a myriad of meanings depending on the context, and it's often the same with German prepositions. Many English phrases that use prepositions are replaced by entirely different structures in German – take the example of “auswendig", translating to “by heart". The reverse is also true. In fact, good use of idiomatic preposition usage is often considered a mark of true fluency. Seeing that there are far too many of these to possibly list in any article, it is advisable that if you have a question with regards to a translation that you ask a native, or failing that, looking it up in an online dictionary that translates idiomatic phrases. (I would personally recommend wordreference.com.)
Accusative Case Prepositions
These basic prepositions always take the accusative case, no matter the situation.
bis – until, up to, no later than*
durch – through, caused by
entlang – along, down*
für – for
gegen – against
ohne – without
um – around
* “entlang" is a bit tricky: it is placed after the object that it modifies, not before the object as with these other prepositions. For example, “Sie rennt die Strasse entlang", translating as “She runs down the street."
Dative Case Prepositions
These prepositions will always take the dative case, no matter the situation:
aus – from, out of
ausser – except for, besides
bei – at, in the vicinity, near*
gegenüber – opposite, across from**
mit – with, by means of
nach – after, to (geographical location)***
seit – since
von – from, (written) by
zu – to, at (people, nongeographical location, direction, desination)****
*“bei" will contract with “dem" to form “beim".
** “gegenüber" can be placed either before or after the object that it modifies.
*** “nach" is usually placed after the object it modifies. It only very rarely requires an article.
**** “zu" contracts with “der" to form “zur" and with “dem" to form “zum". Be careful to differentiate “nach" and “zu".
“Two Way” Prepositions
Here's where it gets tricky. So-called “two-way" prepositions may take the accusative or the dative case, depending on the circumstances. As a general rule, when the prepositions indicate movement of some sort, they take the accusative case, while if they indicate location, they take the dative case. Think of accusative as being the active one. Here are the changeable-case prepositions:
an – at, right by, next to*
auf – on, upon
hinter – behind
in – into**
neben – beside, next to
über – over, above; about
unter – under
vor – before, in front of, ago (time)
zwischen – between
* “an" contracts with “dem" to form “am".
** “in" contracts with “das" to form “ins", and with “dem" to form “im".
Genitive Case Prepositions
These prepositions will similarly always take the genitive case.
(an)statt – instead of*
ausserhalb – outside of
innerhalb – inside of
in der Nähe – near
trotz – despite*
während – during*
wegen – because of*
*In informal spoken German, these prepositions will commonly take the dative case.
Compass directions also take the genitive case:
nördlich – north of
östlich – east of
südlich – south of
westlich – west of