1. to know/learn something by heart 記住；背誦

I can recite this poem without looking at it. I know it by heart.

我不用看就能把這首詩背出來。我已經把它背下來了。

2. to know something like the back of one’s back 了如指掌

He's lived in this city all his life. He knows it like the back of his hand.

他在這座城市住了一輩子，對這里可以說是了如指掌。

3. know something inside out 了解徹底

She spent twenty years studying the history of London. She knows it inside out.

她學了20年的倫敦歷史。對此，她已經了解的十分徹底了。

4. know next to nothing 幾乎不了解；幾乎一無所知

I'm really not interested in politics. I know next to nothing about it.

我對政治實在沒什么興趣，對此幾乎一無所知。

5 .not have the faintest idea 一點都不知道

'Which is the longest river in the world?' 'I haven't the faintest idea.'

“世界上最長的河流是哪條河？”“我沒什么概念。”

6. haven’t got a clue 一點不知道

'Can you tell me where Portsmouth Road is?' 'Sorry, I haven't got a clue.

“你知道樸次茅斯路怎么走嗎？”“抱歉，我不知道。”