Dukes in the United Kingdom
Duke, in the United Kingdom, is the highest-ranking hereditary title in all four peerages of the British Isles. A duke thus outranks all other holders of titles of nobility (marquess, earl, viscount and baron).
Peerages in the United Kingdom
The peerage is a legal system comprising both hereditary and lifetime titles in the United Kingdom (as elsewhere in Europe), composed of various noble ranks, and forming a constituent part of the British honours system.