The prefix 되 means "again" or "back". - 되돌아가다 = went back (without achieving what was intended). (돌아가다 sounds like returning as expected; adding 되 suggests it is unexpected or unusual). - 되찾다 = regain (a lost item). - 되돌아보다 = look back again. (adds emphasis to 돌아보다 = look back) - 되묻다 = ask back/again. - 지난 주에 보낸 택배가 수취인 주소 불명으로 되돌아왔다 = The parcel I shipped last week came back because of unknown recipient address.