One day my friend was kidding me, I replied him "He is naughty."

In Chinese,"Naughty" is a neutral word. Usually use between parents and children; among friends.

But he felt puzzled and started to confirm my meaning with me.

Does "调皮" means that you try to trick people? Or does it means 自作聪明的人？ He told me Naughty= try to trick people or try to do bad things and not allow anybody to know. 100% a negative word in English. Unless they use naughty to talk about sex. Only the sexual definition of naughty is a positive word. Naughty is also used to talk between lovers. If your lover touches you sexually in public, you can call him naughty. It means "now is not the time to touch", in this way it means sexually playful. Which most males belie is a positive use of the word naughty. So naughty is only a word for children who mildly disobey, or for horny lovers.

Then I felt that in USA there are so many words have indirect meanings,especially when it comes to SEX. Maybe because of sex was also an obscure thing,cannot be expressed directly in western countries in the past. As the time goes by, some indirect meaning words became established use meaning. But for other different culture background people, they don't understand them if no one mentioned.

One my provious colleague told me he can't understand that the parents who give girl names use "Cherry".

Even now, I feel confused that "Naughty" only use for female, male or both?
Does lover means 情人 or 爱人? In Chinese 情人 means unwarrantable relationship, but 爱人 means wife or husband. Feeling confused...

That's I called a culture shock. Nobody tell me naughty's indirect meaning in the past, maybe because feeling embarrassing. But if nobody correct you, you will use it in a wrong way all the time. I ever met many foreigners, their Chinese are very well, but they still do misunderstand when they talk to local people. Different culture backgrounds and histories.