Difference between 당신이 잠든 사이 and 당신이 잠든 사이에?

Question

There are two Korean TV shows with titles that were translated as "While You Were Sleeping" in English. What's the difference between them? * 당신이 잠든 사이 * 당신이 잠든 사이에

Answer 1

에 means here “ in, at, on” like “ the time particle”

에 could also be dropped/ omitted in spoken language. People do that a lot. However, I would use 잠든 사이에 just to be on the safe side and grammatically sound