I can write "what a cup is?" as question and I can write "what is a cup?". Are both forms grammatically correct?
The former one looking a bit off when used without context, but I'm planning to use it in a pair like: "What a cup is not?" and "What a cup is?". Stressing on IS rather than on a cup in this case, as I want to stress that definition is important and important when done in comparison to a not part.
Maybe it is sound even better with some adjective rather then noun, like: "What flexibility is not?" vs "What flexibility is?".
But I feel that this is somehow wrong still.