"Why is Kateřina a good wife?"
Translation:Proč je Kateřina dobrá manželka?
You cannot use žena here. It is not clear from the sentence that you mean wife. Žena typically means wife when there is a possessive pronoun before it. JEHO žena, MOJE žena, FRANTIŠKOVA žena. There are very few sentences where you could say žena and mean a wife and it would come out with that meaning in the absence of possession. For example "Čeká na ženu". He is wating for a woman". In English it is some unknown woman, in Czech in this particular sentence if it was some unknown woman one would actually use the word SOME. Čeká na NĚJAKOU ženu. But that is an exception. Follow the possession rule and you should be fine.
Ok. In English, the article "a" is used often, and is discarded in this sentence. The arrangement/inclusion of small words between languages is one thing that gives me the most trouble. For example, languages like Spanish not only include their version of the English article "a", but sometimes include their version of "the" more frequently (i.e., "El, "Ella," "Los", "Las" than we would in English.
Is it safe to assume that in Czech, we can generally drop any translation of the English article, "a"?
As a general rule, I'd say you'd be pretty safe using "a" in English when no demonstrative is used in Czech.
There is no equivalent to the English article "a" in Czech. If there is no demonstrative in the Czech sentence, "a" would be accepted on the English side. Depending on the context, "the" might also be accepted, especially when it is clear, or reasonably so, from the Czech sentence that some specific thing is (or may be) being considered. (That's a bit tricky here, of course, because context is not always apparent...)