(うん) Luck – unlike the others, 運 can be bad OR good
(さいわい) Fortunately (they said our baseball game was going to be rained out, but fortunately it was sunny that day).
(こううん) A lucky son-of-a-bitch. This is the only one you use about people. If you won the lottery AND got married to a guy with five penises, that’s こううん.   PPP
(こうふく) Happiness – generally also means you’re so happy you want everyone around you to have a great day too. Good-will. Amity!!!!