Correct

你知我知,天知地知

/ nǐ zhī wǒ zhī tiān zhī dì zhī /
Strokes
https://i.cchatty2.com/filters:format(webp)/fit-in/684x0/img/202102/你知我知天知地知-Chinese-idioms-Cchatty-7b69470f-30ec-4c04-90b4-8887e574bd96-1612776400.jpg

Collocation

1
只有你知我知,再就是天知地知了
2
这事你知我知,天知地知

Definition

你知我知,天知地知

Literally means:

you know it and I know it, heaven knows and the earth knows

Actually means:

it is a secret between you and me

It means in this world, only you and I know this secret. It stresses that something done by two persons or known only by them cannot possibly be let out to outsiders.

指天地间只有你我两人知道。强调两人所做的或所知道的事别人不可能知道。

Example

Used as predicate or attributive, and it can have other words between the two parts of this phrase. (作谓语、定语,后一部分的前面可以加别的词语)
1
Sòng
qián
zhèzhǒng
这种
shì
jiǎndān
简单
  
,
zhī
zhī
  
,
tiānzhīzhī
天知地知
  
,
háiyǒu
还有
shuí
zhīdào
知道
ne
  
?

Send money this kind of thing is simple, you know I know, heaven knows, who else knows?

2
Zhè
jiàn
shì
zhīyǒu
只有
zhī
zhī
  
,
zàijiùshì
再就是
tiānzhīzhī
天知地知
liǎo
  
,
zhǐyào
只要
men
我们
shuō
  
,
shì
huì
不会
yǒurén
有人
zhīdào
知道
de
  

This matter only you know I know, then god knows, as long as we do not say, no one will know.

3
Jīntiān
今天
de
shì
  
,
méiyǒu
没有
sānzhě
第三者
zàichǎng
在场
  
,
zhīyǒu
只有
zhī
zhī
  
,
tiānzhīzhī
天知地知
  
,
yǒu
shénme
什么
hǎo
dānxīn
担心
de
ne
  
?

Today's matter, there is no third party present, only you know I know, heaven knows, what do you have to worry about?