他们感到快乐的英语是 "They feel happy."

这个短语的来源可以追溯到拉丁语,其中 "feel" 来自 "sentire",意思是 "感觉","happy" 来自 "fepx",意思是 "幸福的"。

下面是一些英文例句,并提供中文翻译:

"They feel happy after winning the game." (他们在赢得比赛后感到快乐。)
"I could tell they feel happy just by looking at their faces." (我可以从他们的表情看出他们感到快乐。)
"The news made them feel happy and repeved." (这个消息使他们感到快乐和解脱。)