Relative Pronouns (der, die, das, welcher, welche, welches)
How do relative pronouns work and decline?
Relative pronouns introduce relative clauses and refer back to a noun in the main clause. They agree in gender and number with the noun they refer to, but their case is determined by their function within the relative clause.
Declension: They decline like definite articles, but the genitive plural is deren (for feminine/plural) and dessen (for masculine/neuter singular). Welcher/welche/welches also decline like definite articles.
Das ist der Mann, der mir geholfen hat. (Nom. Masc. - der refers to Mann, is subject in relative clause)
Das ist die Frau, die ich gesehen habe. (Acc. Fem. - die refers to Frau, is direct object in relative clause)
Das ist das Kind, dem ich das Spielzeug gab. (Dat. Neut. - dem refers to Kind, is indirect object in relative clause)
Das ist der Autor, dessen Buch ich lese. (Gen. Masc. - dessen refers to Autor, shows possession)