knows

know, know about, know of

这三者都有“知道,了解”的意思。它们的区别是:know 表示直接地知道,熟知；而know of 是间接得知(听人讲过,从书报上看过等); know about指知道关于某事的情况。例如:

I know of him, but I don't know him personally.我听说过他,但不认识他。

It is better to know one thing than to know about ten thousand things.熟知一事要比略知万事要好。

know by, know to

这两个短语的区别很细微:

1.know to的意思是“为大家所了解”, know by的意思是“被大家所熟知”。现代英语中be known to较少使用。例如:

He's known to everybody here.

这里的人都熟悉他。

He's known by everybody here.

这里的人都了解他。

2.know by的主动形式往往用于表示认识人〔事物〕的手段或标准。例如:

We know a judge by the clothes he wears.我们可以根据他穿的衣服认出法官。

know, learn, understand

这组词都有“了解”的意思。它们的区别是:know指对某一事物的直接了解或通过体验、传授获得知识; learn意为“听说”“得知”,强调对某一具体事物从“不知”到“知”的变化; understand指对某事物的性质、规律、意义等都十分了解,而且还指了解它所包含的其他意义和关系,其程度要比know了解得更深、更广。例如:

How had he learned that secret?他怎么得知这个秘密的?

They were greatly surprised to learn the news.听到这个消息,他们都很吃惊。

Do you understand the difficulty of my position?你了解我处境的困难吗?