Why is the Bishop called your Grace?

Answer 1

Anglican Bishops (not Roman Catholic clergy) are referred to as "Your Grace." However, in parts of the world where Anglicanism is predominant the Roman Catholic clergy allow the use of Your Grace so that the general population who are not catholic are not confused about titles of address.

For Roman Catholic Bishops....

In spoken conversation, you would call your bishop "Bishop (last name)" or "Your Excellency." In opening a letter, you would put "Dear Bishop (last name)" or "Your Excellency" ("Dear" is not used in front of "Your [title]"). In addressing an envelope you would put on the first line "The Most Rev. (full name)" and on the second line "Bishop of (diocese)."

Archbishops follow the same protocol as bishops. Cardinals are addressed as "Cardinal (last name)" or "Your Eminence." Letters to cardinals open "Dear Cardinal (last name)" or "Your Eminence." In addressing the envelope the first line would read "(first name) Cardinal (last name)" or "Cardinal (full name)"; the second line would read "Archbishop (or Bishop) of (archdiocese or diocese)."