사랑이 뭐예요? or saying 사랑은 뭐다? " mm...simply, Beth, 사랑은 뭐다 is very strange expression. it's like declaritive ending with just question mark. Korean is a bit different from European languages, so needs proper ending particle such as ~까, 요?, 니? and so on for question. sometimes we can use declaritive ending, at that time it's very special circumstance. When your teacher give you THE definition of something, such as '책은 마음의 양식이다(Books are food for the mind), and then she can ask back to us like '책은 무엇이다?' then we can say '마음의 양식(이요)'. so when you say, 사랑이 뭐예요? means What is the Love? when you say '사랑은 뭐다?' can be meant to check it out all over again after you gave the definition from the first to someone. make sense? it is not really normal sorta expression or situation, so I rather say you can stick to '사랑이 뭐예요' or '사랑이 뭐지요?' or '사랑은 뭘까?' or '사랑이 뭐라고 생각해?' have a good weekend, :) hope it could help you out a bit .