on purpose
英 [ɒn ˈpɜːpəs]   美 [ɑːn ˈpɜːrpəs]  
故意地，特意地，有意地

例句：
I didn't do it on purpose - it was an accident. 

我不是故意的，那完全是个意外。

If you joke with him he'll think you're insulting him on purpose. 

如果你同他开玩笑，他就会认为你在故意侮辱他。

You sometimes hurt yourself by accident but you don't hurt yourself on purpose. 

你有时会偶然地伤害自己，但你不会故意地伤害自己。

Was it an accident or did David do it on purpose? 

是意外还是戴维故意所为？