Peerage of England
The ranks of the English peerage are, in descending order, Duke, Marquess, Earl, Viscount, and Baron. While most newer English peerages descend only in the male line, many of the older ones (particularly older baronies) can descend through females. Under English inheritance law all daughters are co-heirs, so many older English peerage titles have fallen into abeyance between various female co-heirs.
Hereditary peer
A title held by someone who becomes monarch is said to "merge in the Crown" and ceases to exist, for the Sovereign cannot hold a dignity from himself. The Dukedom of Cornwall and of Rothesay, and the Earldom of Carrick, are special cases, which when not in use are said to "lapse to the Crown": they are construed as existing, but held by no one, during such periods. These peerages are also special because they are never directly inherited. The Dukedom of Cornwall was held formerly by the eldest son of the King of England, and the Dukedom of Rothesay, the Earldom of Carrick, and certain non-peerage titles (Baron of Renfrew, Lord of the Isles and Prince and Great Steward of Scotland) by the eldest son of the King of Scotland. Since those titles have been united, the dukedoms and associated subsidiary titles are held by the eldest son of the monarch. In Scotland, the title "Duke of Rothesay" is used for life. In England and Northern Ireland, the title "Duke of Cornwall" is used until the heir-apparent is created Prince of Wales. At the same time as the Principality is created, the Duke is also created Earl of Chester. The earldom is a special case, because it is not hereditary, instead revesting or merging in the Crown if the Prince succeeds to the Crown or predeceases the monarch: thus George III was created Prince of Wales and Earl of Chester a month after his father's death.