いかんせん

An adverbial idiomatic expression conveying the feeling "unfortunately, nothing can be done." It shows a limit or regret: one wants to do it or wishes it were so, but because of some circumstance it cannot be realized. It originally derives from 「いかにせん」 (what should one do). It is often placed at the head of a sentence or clause. Its meaning is close to 「いかんともしがたい」, but it differs in that it functions as an adverb stating the circumstances. A somewhat old-fashioned, formal word.