Language has changed from English to Chinese

Go to "apple" menu and go to system preferences, click on international ( the icon with the UN flag), from there you can change your preferable language. if english, Drag english all the way to the top of the list on the left. The list basically, means the other that your mac is going to select a language, if is not available for that particular one, it goes down the list. In the menu, order for sorted list, select english. on the last setting, word brake, leave it at standard.
I hope that was what you were referring to, if not, be a bit more specific. for example. are you referring to your mac in general or a specific program on your mac.
Otherwise, that should do the trick.