如果你笑，世界也会陪你一块欢笑。

Laugh, and the world will laugh with you.

youdao

如果你笑累了，可以坐下来歇歇，喝杯咖啡，那将是多么惬意的事情。

If you are tired smile, you can sit down and rest, a cup of coffee, how it would be nice.

youdao

如果一个性感妞儿向你挑逗，你应该一笑走开。

If a hot chick comes on to you, smile and walk away.

《柯林斯英汉双解大词典》

Now if you smiled to-- or make three people smile, and these three people-- each one makes three other people smile.

如果你的笑-,感染了三个人，这三个人-,每个人又引起另外三人发笑。

哈佛公开课 - 幸福课课程节选

Children are particularly influenced by the contagiousness of laughter, but just in general, if you hear somebody laughing, like the kids you saw before, it's the sort of thing that could easily make you laugh.

孩子特别容易,受笑声的感染，但普遍来说，如果你听到有人笑，像你们刚才看到的小孩子，这样的事物很容易引你大笑。

耶鲁公开课 - 心理学导论课程节选