This is the 999th most frequent Croatian word.
kakvu
"What kind" or "what type of" (feminine singular accusative form).
Here, 'kakvu' is used to indicate the extraordinary nature of the noun 'sreću' (happiness) experienced.
Ne možeš zamisliti kakvu sam sreću osjetio!
You can't imagine the kind of happiness I felt!
In this sentence, 'kakvu' functions as an interrogative adjective describing the noun 'haljinu' (dress), asking for a characteristic or type of the dress.
Kakvu haljinu misliš kupiti?
What kind of dress are you thinking of buying?
In this context, 'kakvu' acts as an interrogative adjective describing the unknown quality or type of the noun 'hranu' (food).