Interrogative pronouns

The interrogative pronouns wer, was, welcher and  was für ein lead off a direct or indirect interrogative clause:

Wer hat morgen frei? Who has the day off tomorrow?
Weißt du, wer der Mann da ist? Do you know who that man is over there?
Was für ein Auto möchtest du? What kind of car would you like?

The pronoun wer

Nom. wer Wer bist du?  Who are you?
Acc. wen Wen siehst du da? Whom can you see over there?
Dat. wem Mit wem sprichst du? To whom are you talking?
Gen. wessen Wessen Buch ist das? Whose book is this?

The pronoun wer is identical in the singular and plural. There is no separate plural form:

Wer kommt mit? Who is coming?
Rosa kommt mit.
Alle kommen mit.
Rosa is coming.
Everyone is coming.

The pronoun was

The pronoun was always occurs in the same form.

Was hat sie dir erzählt? What did she tell you?

Was is not used together with prepositions. Instead, use the pronominal adverb wo(r) + preposition.  

Wovon sprichst du eigentlich? What are you actually talking about?
Woran denkst du? What are you thinking about?


An wen denkst du? Who are you thinking about?

Was für ein and welcher

was für ein/ein/eine; plural was für what kind of?
welcher, welches, welche; plural welche which?

Use was für ein to ask what something is like. The last part of the pronoun, ein, declines just like an indefinite article. The answer normally leads off with an indefinite article (if in the singular): 

Was für ein Auto möchtest du?
Ein kleines.
What kind of car would you like?
– A small one.

The pronoun welcher (which) declines just like dieser:

  Masculine Neuter Feminine Plural
Nom. welcher welches welche welche
Acc. welchen welches welche welche
Dat. welchem welchem welcher welchen
Gen. welchen welchen welcher welcher

Welcher requires a choice between two or more options, hence the answer normally leads off with a definite article:

Welcher Bus fährt zum Flughafen?
– Die Nummer 62.
Which bus goes to the airport?
The number 62.
Welches Auto (von den beiden) möchtest du?
– Den Mercedes natürlich.
Which car (of those two) would you prefer?
– The Mercedes, of course.