"What is quality?"
Translation:Co to jest jakość?
"Co jest jakość?" doesn't make sense, "Co jest jakością?" - seems rather weird, "Czym jest jakość?" is perfectly fine. But in the default version, "to" is needed. "jest" may be omitted, but I'd recommend keeping it.
The best way to write this would be: Co to jest "jakość"? - as in fact, you are asking for a definition of a word.
Yeah you're right, we could say Ćto eto kaciestwo, or Kaciestwo eto ćto, so Co to jakość would've made sense to me. I was thinking in English with jest="is" but I forgot about the instrumental case after być--big mistake, but I agree that the instrumental doesn't work in this case, Ćto jest kaciestwom?
We wouldn't say Ćto eto jest' kaciestwo or Ciem jest' kaciestwo in Russian, though. The best usage would be Ćto znacit kaciestwo?.