Grace (style)
His Grace or Her Grace is a style used for various high ranking personages. It was the style used to address the King or Queen of Scotland up to the Act of Union of 1707, which merged the Kingdom of England and the Kingdom of Scotland, and to address monarchs of England prior to Henry VIII. Today, the style is used when referring to non-royal dukes and duchesses in the United Kingdom.
For example, His Grace The Duke of Norfolk, or His Grace The Archbishop of Canterbury; or Your Grace in spoken or written address. Royal Dukes, for example The Duke of York, are addressed with their higher royal title, Royal Highness.
Ecclesiastical usage
The style "His Grace" and "Your Grace" is used in England and other English-speaking countries to address Roman Catholic archbishops. In the Eastern Orthodox Church it is used for bishops and abbots. The style is also used for an archbishop and some bishops in the Anglican tradition. In the United Methodist Church, Bishops are addressed Your Grace (spoken style), and His/Her Grace (reference style).