no. the question has to be in the case the answer will be. (Or as a Polish person sees it, the answer has to be in the case the question is asked- we know questions not names of cases)
Yes, in fact it makes more sense, czego would be interprited as "why do you not eat"
No. "co" is a wrong case of "what", "czego" means "what", you got it confused with "dlaczego".
What do you not eat is not very correct English, unless it's a question of what food you will leave on the plate. Did you mean why are't you eating which would be proper.
"What do you not eat"/"What don't you eat" seem fine to me. Person 1: "I am a vegetarian". Person 2: "Oh! What do you not eat?". P1: "Anything made of meat". P2: "Oh! OK".
I agree it is valid English, but "What do you not eat?" sounds less natural to me because it injects the pronoun (you) between what would naturally become a contraction (do not -> don't).
It sounds almost like a mechanical translation in which a computer was trying to obey a rule to put "not" next to "eat" and "do" immediately after "What." This yields a technically valid sentence because "you" can't go anyplace else once it applies those two rules. Nevertheless, it is a much more common practice to form the contraction.
Czego nie jesz? (or even better: Czego nie jadasz?) is in fact the question you mentioned in the first sentence of your post.
is that "dla czego" is pretty rare, but it means "for what", and "czego" is a Genitive form of "what".
And "dlaczego" means "why".
Why doesn't dlaczego change case when used in negative ie dlaczego nie? why not?
"Dlaczego" indeed turns into "dlaczego nie" to translate "why not?".
Or wasn't that what you meant?
Always wondered why Poles are so smart, mastring all the vagaries of the language should get you a PHD. or at last a Masters degree.
Not sure the translation is correct; shouldnt it be translated as "why aren't you eating?"
Colloquially, you might say in Russian: "Чего ты не ешь?" But in Polish you'll need dlaczego or czemu if you want the sentence to have this meaning.
It's my job here to point out to Russian native speakers that Polish grammar doesn't always work like Russian :)
Actually I think that "Czego" may be a colloquial form of "Dlaczego", not very common though.
The question word is "czego", which is the genitive of "co". So it is "what don't you eat?", and the genitive is used here as we have a negative verb.
"Why?" is "dlaczego?"
As I interpret it, czego would be what don't you and dlczego would be why don't you, correct?
That would be my understanding of the standard interpretations of these two words if used in this negative sentence. "DlAczego", BTW.
With a little brainstorming we can often come up with a reasonable alternative, I'm a lousy tyist not speller. Most of my errors are made because of this, and with my big paws, tend to hit two keys at a time.