orbiter wrote:What does "이여서" mean when it is used at the start of a sentence? I always hear the radio DJ use this, but I've not come across this except when it is in the middle of a sentence e.g. "당신이여서", or "내생일이여서"...
Does it mean "therefore", by any chance?
I think it should be '당신이어서' and '내 생일이어서'.
And it means as you guessed, "therefore" or "because..."
Actually it can be break down into 이 + 어서. (이 from _이다 verb)
If you use that ending right next to _하다 verbs, 어서 should be changed into 여서.
...하여서