know someone by sight

跟某人面熟

►含义：

recognize someone by their appearance without knowing his or her name

通过长相能认出某人但不知对方名字

►例句：

I know him by sight but have never spoken with him. 

我跟他面熟，不过从没说过话。

►对话：

A:Do you see that guy over there? What’s his name?

你看到那边的人了吗？他叫啥？

B:I know him by sight, but I don’t know his name.

我只是看他面熟，但我不知道他叫什么。

►额外收获： 

1.recognize: vt.认出

2.speak with sb.: 跟某人说话