OS X default input language I have three languages in macOS Sierra. I want to set a default one, when I open new window in browser, for example, English. 

Usually it's so but sometimes it's another one that I use rarely. And I can't understand when it's English and when another one. 
I'm new to Mac, in Windows there is default language option. Is there some option like this in macOS?
You keyboard input language is controlled by system preferences/keyboard/input sources and what you select in the "flag" menu in the Menu Bar (not by Language and Region).  Check your settings there.