Change 'Username' to 'Email' in log in

I'm trying to change 'Username' to 'Email' in the log in section on the initial page. I already changed all language keys related (including '_NickName') Nothing worked. A step by step solution would be greatly appreciated.

Please see file attached for reference. 

Change username to email or username or Email

     http://your-site.com/administration/lang_file.php?filter=username 

Everything working now. I guess I needed to clear cache.