Relative pronouns are used in relative clauses. These are clauses that are used as additional commentary about a noun from another clause in a sentence. In English, the relative pronouns are: that, which, who, whom, and whose. German has more relative pronouns; in fact, there is a relative pronoun for every gender and case, and they only differ in one instance from the definite articles: in the dative plural (“denen” instead of expected “den”). Here are the relative pronouns:
Relative clauses in German are dependent clauses, which means that they follow dependent word order (i.e. the verb is moved from second to final position). Relative clauses can occur right after a subject or predicate noun (the antecedent), and the relative pronoun refers back to the antecedent, though it can have a different grammatical function in the relative clause. If the relative clause follows the subject (see second example below), for the purpose of word order, it is considered an aside (sidebar comment) and is set off by commas without interrupting word order of the main clause. Relative pronouns can be combined with prepositions, in which case the preposition precedes it. Here are a few examples of relative clauses:
Das ist der Mann, mit dem ich gesprochen habe. / That is the man with whom I was talking.
Die Stadt, in der ich lebe, heißt Dresden. / The city in which I live is called Dresden.
Ich sehe eine Frau, der ich Geld geliehen habe. / I see a woman whom I loaned money.