- 你知不知道他们是谁?
Do you know who they are?
- 玛莉亚既不知道他的名字，也不知道他的电话号码。
Maria knew neither his name nor his phone number.
- 她问我知不知道他的地址。
She asked me if I knew his address.
- 我知道他的名字，但不知道他长什么样。
I know him by name, but not by sight.
- 知者不言，言者不知。
He who knows does not speak, he who speaks does not know.
- 以前的人不知道地球是圆的，也不知道地球是绕著太阳转的。
Formerly people did not know that the earth is round and that it moves round the sun.
- 谁也不知道为甚么。
Heaven knows why.
- 我不知道该怎么办。
I have no idea of what to do.
- 很多经济学家都不知道这点。
Many economists are ignorant of that fact.
- 谁也不知道将来会发生甚么事。
There is no telling what will happen in the future.
