your grace

Short definition from Wiktionary

Pronoun

1. 1
   A title of respect used when addressing a duke or duchess or other high noble of equivalent rank.
2. 2
   you (as a polite form of address to social superiors)

Noun

1. 1
   Used in direct address to archbishops.
2. 2
   Used in direct address to bishops, although in British English sometimes only granted to the Bishop of Meath and Kildare in Ireland.
3. 3
   Used in direct address to dukes and to Lord High Commissioners.