know后面加什么介词?为什么要加这个介词?最好写得详细一点,有例子最好.

know about
这个是固定搭配，没有为什么

know [nəu]
vt.知道,了解,懂得,通晓,掌握…的知识(或技能)：Does he know English?他懂英语吗?I know the facts.我了解事实情况.He knows how to play chess.他会下棋.确知,确信,确认：I know that he's a good man.我确信他是个好人.认识；相识,结识：I never know such a man.我从不认识这样一个人.He knows my brother.他认识我弟弟.I know of him, but I do not know him personally.我听说过他,但我并不认识他.

BE FAMILIAR WITH 熟悉
know:
1. [ not continuous] to be familiar with or have experience and understanding of:[不持续] 熟悉或有过交往和了解
I've known Daniel since we were at school together.
自我们一起上学时,我就认识了丹尼尔.

2.[ not continuous](ALSO know about) If you know a subject, you are familiar with it and understand it:
[不持续](也用know about) 如果说你know 一门学科,那你就是熟悉和了解那门学科.
Do you know about computers?
你熟悉电脑吗?
She knows her subject inside out
她完全熟悉她的学科.

知道:
3.I don't know anything about this.

例句翻译自：
(from Cambridge Advanced Learner's Dictionary)



总结:
1.know认识----了解
2.know about 熟悉------掌握
2.know sth. about it知道