I'm mid-homework and I came upon following sentence: "Seine Mutter ist (nurse)." Should I write "die", "eine" or simply "Krankenschwester"? And why?
If you want to point at one specific nurse or there is just one then "die Krankenschwester" is the correct term. -> His mother is the nurse.
Otherwise you want to say "(eine) Krankenschwester". If you just want to say the job/profession you can omit the "eine", that is what I mean by using paratheses. -> His mother is a nurse. As far as I know it is never wrong if you don't omit it, though.
I dont know if my explanations are understandable, tell me if anything is unclear.