The genitive case is used to indicate possession, like of or apostrophe-s ('s) does in English. However, apart from in formal, written texts (and in its version of adding 's, which is just to add an s to the end of proper nouns), German tends to avoid the genitive. Most of the time in spoken German, Germans use a von plus the dative instead of a genitive to mean of. The genitive is unusual in German, because as well as affecting determiners (words like the and a) and adjectives, it also affects nouns, adding an -s (or -es) to the end of neuter and masculine nouns.
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