Wiktionary
your grace
n. 1 (context Christian English) (non-gloss definition: Used in direct address to archbishops). 2 (context Especially Eastern Orthodox Christian English) (non-gloss definition: Used in direct address to bishops, although in British English sometimes only granted to the Bishop of Meath and Kildare in Ireland.) 3 (context UK English) (non-gloss definition: Used in direct address to dukes and to Lord High Commissioners.)
your grace
pron. (context formal obsolete English) you
Usage examples of "your grace".
I know it was an impudence, and felt it one, your Grace, but I plucked up courage to—.