Interrogative adjectives (soru sıfatları) are used to ask questions about nouns. They always precede the noun they modify.

Main Interrogative Adjectives:

• Hangi: Which?
  Example: Hangi kitabı okuyorsun? (Which book are you reading?)
  Example: Hangi ev daha güzel? (Which house is more beautiful?)
• Nasıl: What kind of? / How? (when describing a noun's quality)
  Example: Nasıl bir araba aldın? (What kind of car did you buy?)
  Example: Nasıl bir insan o? (What kind of person is he/she?)
• Kaç: How many? (used with countable nouns)
  Example: Kaç elma var? (How many apples are there?)
  Example: Kaç kişi gelecek? (How many people will come?)
• Ne kadar: How much? (used with uncountable nouns or for price/quantity)
  Example: Ne kadar süt istersin? (How much milk do you want?)
  Example: Bu elbise ne kadar? (How much is this dress?)
• Ne: What? (can act as an adjective in certain contexts, often asking about type or identity)
  Example: Ne renk boya aldın? (What color paint did you buy?)
  Example: Ne iş yapıyorsun? (What job do you do?)

Like other adjectives, interrogative adjectives do not change for number or case. The noun they modify, however, can.