1.
A relative clause gives more information about a noun that has been mentioned in a previous part of the sentence, e.g.
Der Hamburger Dom ist ein großes Volksfest. (The Hamburger Dom is a huge amusement fair.)
Der Hamburger Dom ist ein großes Volksfest,
The Hamburger Dom is a huge amusement fair which takes place three times a year.
relative clause
A relative clause is a type of subordinate clause, i.e. it can not exist on its own. Remember that, in a subordinate clause, the conjugated part of the verb moves to the end of this clause.
Er kommt nie zu spät zur Arbeit. (He is never late for work.)
Das ist ein Student,
This is a student who is never late for work.
3.
A relative clause starts with a relative pronoun which German, unlike English, can never omit, e.g.
Is that the man (whom) you saw yesterday in the bank?
r e l a t i v e c l a u s e
Ist das der Mann,
du gestern in der Bank gesehen hast?
relative pronoun
5.
The relative pronoun has the same gender (masculine, feminine or neuter) and number (singular or plural) as the noun it gives more information about, but its case depends on its function in the relative clause, e.g.
5.1
fem. sing.
↓
Belen ist eine deutsche
Firma,
die
the relative pronoun takes on the role of the subject in the relative clause, therefore it has to be in the nominative case -> nominative/feminine/singular -> "die"
5.2
neut. sing.
XYZ ist ein deutsches
das
XYZ is a German company which produces solar cells.
the relative pronoun takes on the role of the subject in the relative clause, therefore it has to be in the nominative case -> nominative/neuter/singular -> "das"
5.3
masc. sing.
Das ist sein
den
the relative pronoun takes on the role of the direct object in the relative clause, therefore it has to be in the accusative case -> accusative/masculine/singular -> "den"
5.4
plural
Hier sehen Sie die
he relative pronoun takes on the role of the direct object in the relative clause, therefore it has to be in the accusative case -> accusative/plural -> "die"
5.5
Das ist mein
dem
the relative pronoun takes on the role of the indirect object in the relative clause, therefore it has to be in the dative case -> dative/masculine/singular -> "dem"
5.6
Wie heißt die
der
the relative pronoun takes on the role of the indirect object in the relative clause, therefore it has to be in the dative case -> dative/feminine/singular -> "der"
5.7
Herr Bauer,
dessen
↑
the relative pronoun is part of the genitive (dessen Frau = whose wife) ->
genitive/masculine/singular -> "dessen"
5.8
Die Katze,
deren
the relative pronoun is part of the genitive (deren Halsband = whose collar) ->
genitive/feminine/singular -> "deren"
6.
The parcel which you were waiting for has arrived.
preposition
Das Paket,
auf
Sie gewartet haben,
ist angekommen.
7.
7.1
Warum rufen Sie nicht Ihren
the relative pronoun comes after "von"; this preposition is always followed by the dative case -> dative/masculine/singular -> "dem"
7.2
Meine ehemaligen Kollegen,
denen
the relative pronoun comes after "zu"; this preposition is always followed by the dative case -> dative/plural -> "denen"
7.3
Das ist meine
the relative pronoun comes after "ohne"; this preposition is always followed by the accusative case -> accusative/feminine/singular -> "die"
7.4
Ich möchte in einem
the relative pronoun comes after "in"; in this case "in" is followed by the dative case since you can only ask "where?" and not "where .... to?"-> dative/neuter/singular -> "dem"
7.5
Der Schreibtisch hat nur eine kleine
Schublade,
the relative pronoun comes after "in"; in this case "in" is followed by the accusative case since you can ask "where ... to?"-> accusative/feminine/singular -> "die"
plural.
Kennst du die
the relative pronoun is part of the genitive (deren Haus = whose house) -> genitive/plural -> "deren"