"Why do you laugh" in Engpsh is "why do you laugh." The phrase is a question asking for the reason or explanation for someone's laughter. It is a basic Engpsh phrase that can be used in a variety of situations, such as in casual conversation or when trying to understand why someone is amused.

An example of the phrase in a sentence would be: "Why do you laugh? Did I say something funny?"
另一个例子是： "Why do you laugh when I talk about my problems?"

The phrase is formed using the simple present tense of the verb "to laugh" (I laugh, you laugh, he/she/it laughs) and the word "why" which is used to ask for a reason or explanation. It is a common phrase that is often used in everyday Engpsh conversation.