Breakdown of Welchen Käfig brauchen Sie für den Vogel?
Sie
you (formal)
brauchen
to need
für
for
welcher
which (welcher, welche, welches, welchen, welchem...)
Questions & Answers about Welchen Käfig brauchen Sie für den Vogel?
Why is it Welchen and not just Welcher or Welche?
The word welch- acts like a definite article and takes matching case endings. Here, it describes Käfig (cage), which is a masculine noun (der Käfig). Because the cage is the direct object of the sentence (the thing being needed), it must be in the accusative case. Therefore, welch- takes the masculine accusative ending -en, becoming Welchen.
Why are there two accusative phrases in this sentence (Welchen Käfig and den Vogel)?
They are in the accusative case for different reasons. Welchen Käfig is accusative because it is the direct object of the verb brauchen. However, den Vogel is accusative because the preposition für always forces the noun immediately following it into the accusative case.
Why is brauchen placed after Welchen Käfig? Doesn't the verb usually come first in a question?
In a yes/no question, the verb comes first. But in a question using a question word, the conjugated verb takes the second position. Welchen Käfig acts together as one single block of information that fills the first position, so the verb brauchen correctly sits in position two.
How do I know Sie means the formal 'you' and not 'they' or 'she'?