master your english !

master oprócz bycia rzeczownikiem słówko to może wystąpić jako czasownik, a oto co wtedy oznacza:

master vt 1. (learn, become proficient in) opanować 2. (control) zapanować (nad kimś/czymś), pokonać

You can master a language, a theory, basics and a technique. 
Ben took on the challenge of trying to master a Japanese. 
A technique of making good photos was surprisingly difficult to master. 
Master your emoitions!

masterly adj mistrzowski 

Henry has a masterly command of the English language. (command = knowledge)