How do I permanently delete fontbook from mac (Sierra OS)? When I try to drag to trashcan, it says it's a system app that is required by os. 

How do I bypass this check and remove the app?
There are instructions for removing font book on this page

http://www.jklstudios.com/misc/osxfonts.html#fontfolderlocations

If you just want it hidden, there's always a chflags command to hide it. You need to bypass SIP restrictions on that folder before you can delete or change the flags to hide it, so it's not going to be quicker than removing it - just easier to undo if you find you or another program needs it at a later date.

ls -laO / &amp;&amp; ls -laO /Applications | grep Font


The first listing shows the variety of flags (hidden, sunlink, restricted, uchg) and the second shows Font Book is restricted from change even by root.

https://derflounder.wordpress.com/2015/10/01/system-integrity-protection-adding-another-layer-to-apples-security-model/