And I found that even scientists don't always agree, and they sometimes use the words "joy" and "happiness" and "positivity" more or less interchangeably.
과학자들 사이에서도 의견이 분분해서 “즐거움”, “행복”,  “긍정” 이라는 단어를 간혹 섞어 쓴다고 해요.