>>>>>>Then the proper question would be "which door is this"... but what if you wanted to ask what was the door of - is it wooden or iron or plastic... "kakva su ovo vrata?". "What kind of door is this" is not good enough, since I think you'd be PO'd both royally and republicly if you had tried all kinds of, say, fishing rods, and you ask "do you have any other kind", and they give you the same old just made of a different type of plastic. That's not a different kind, is it?
>>>>>
>>>>>You'd ask, "Whats' this door made of?"
>>>>
>>>>And get the answer "wooden"?
>>>
>>>No, and get the answer, "wood".
>>
>>So, not the question I was looking for.
>
>So, in fact, you're looking for a question to which you already have the answer, and you want to know precisely how to word the question to get the answer you already have?

Yes, because I see no other way of conveying the meaning of the word - it's a querying pronoun, so to say, like "what", "which", "who", "where", and as much as the "who" demands a person in the answer, "which" demands one out of a set, so should this word demand a quality, property... an adjective. So when you ask "--- is the weather", you get a "good", "lousy", "hot"... but not "it's a physical phenomenon studied by meteorology". The trick question for kids was "--- is a black man when he dives out of the Red sea" - the answer would be "wet" (but every now and then a kid would fall for it and say "red" or "black").

Also, alternate line of getting to this word. There are pairs between such pronouns and their answers, like when - then, where - there, which one - that one, and we miss the question side for "such".