This is useful to know when writing stories.

Words

오래 - a long time ( Noun )

오래오래 - a long long time ( Adverb )

행복하게 - happily ( Adverb )

행복하다 - Happy ( Adjective )

행복 - Happiness ( Noun )

Phrases

오래오래 행복하게 살았답니다 - lived happily ever after ( Formal polite )

한국언니가 동영상 안 올린지 오래 됐다 - It's been a while since Korean Unnie has uploaded a video ( Informal casual )

이거 하는데 그렇게 오래 걸렸어? - It took that much time to do this? ( Informal casual )

오랜 날 오랜 밤동안 그댈 사랑했어요. - For long days and long nights i loved you. ( Informal polite )

나는 행복하다 - I am happy ( Informal casual )

너는 행복하니? - Are you happy? ( Informal casual )

살았답니다 / 살았습니다. - lived ( Formal polite )