Relative pronouns: der, die, das again

The table

Here is the full set. The forms that differ from the definite article are in bold.

Five new forms, and they cluster. The genitive row is new throughout (dessen for masculine and neuter, deren for feminine and plural), and the dative plural lengthens den to denen. Every other cell is identical to the article. If you already have the four cases in your head, this table is a quarter of an hour's work.

Two decisions, made in two places

Choosing a relative pronoun means answering two questions, and the answers come from different parts of the sentence.

1. Gender and number: look back at the noun. der Mann is masculine singular, so the pronoun will be a masculine singular form. die Kinder is plural, so the pronoun will be plural.
2. Case: look inside the relative clause. What does the pronoun do there? Subject, direct object, indirect object, owner?

Watch the same noun take four different pronouns, while the main clause stays exactly the same:

Der Mann, der dort steht, ist mein Vater. - The man who is standing there is my father.

Der Mann, den ich sehe, ist mein Vater. - The man (whom) I see is my father.

Der Mann, dem ich helfe, ist mein Vater. - The man (whom) I am helping is my father.

Der Mann, dessen Auto hier steht, ist mein Vater. - The man whose car is here is my father.

In every sentence the man is the subject of is my father. That is irrelevant. In the first relative clause he does the standing (nominative, der). In the second he is the thing I see (accusative, den). In the third he is the person helped, and helfen takes the dative (dem). In the fourth he owns the car (genitive, dessen).

This is the single most common error with German relative clauses, and it is always the same one: copying the case of the main-clause noun into the pronoun. Cover the main clause with your thumb and ask what the pronoun is doing in the part you can still see.

English is less help than it looks here. Who, whom and whose are the same idea (subject, object, owner), but most English speakers dropped whom from speech a generation ago, so the instinct German needs has been out of use for a while.

The verb goes to the end, and the commas are compulsory

A relative clause is a subordinate clause, so the conjugated verb goes to the very end of it:

Das ist das Buch, das ich morgen lesen will. - That is the book I want to read tomorrow.

Das ist der Film, den ich gesehen habe. - That is the film I have seen.

With a modal or a perfect tense, the conjugated verb (will, habe) goes after the infinitive or participle, last of all. Subordinate clauses sets out why, and it is the same eviction rule that weil and dass trigger.

Commas are not optional in German, and relative clauses are where that bites. A comma always goes before the relative pronoun, and another closes the clause if the main sentence carries on after it. English lets you write the man I saw yesterday is here without a single comma. German writes Der Mann, den ich gestern gesehen habe, ist hier. and would mark the comma-free version wrong in any exam.

You cannot drop the pronoun

English leaves out that and whom all the time: the book I read, the woman I love. German cannot:

das Buch, das ich lese - the book (that) I am reading

die Frau, die ich liebe - the woman (whom) I love

If you translate straight from English, the pronoun is the word you will forget, because English never made you say it. Build the habit of saying the comma in your head, then the pronoun.