"笑口常开"的英文翻译是"always laughing."这个短语源于中文，指一个人经常高兴，开心地笑。

例句：

He was always laughing, even in the face of adversity.

(他总是笑口常开，即使面临逆境。)

She had a contagious smile and was always laughing.

(她有一个传染性的微笑，笑口常开。)

I always feel better when I'm around people who are always laughing.

(我在笑口常开的人身边时总感觉更好。)