Hvilken, hvilket, hvilke and denne, dette, disse

Hvilken (which) and denne (this) agree with the noun that follows:

• en-noun: hvilken / denne, as in Hvilken bus? (Which bus?) and denne jakke (this jacket)
• et-noun: hvilket / dette, as in Hvilket hus? (Which house?) and dette brev (this letter)
• plural: hvilke / disse, as in Hvilke bøger? (Which books?) and disse sko (these shoes)

Some nouns, such as sko or år, look the same in the singular and the plural, so the rest of the sentence tells you which form to use.

In everyday speech Danes mostly say den her, det her, de her instead of denne, dette, disse, which sound more written: den her jakke, det her brev, de her sko. Hvilken is used in speech and writing, but casual talk often has hvad for en / hvad for et / hvad for nogle.