An Earl is the third highest rank of peerage below Duke and Marquess. The title of Earl is derived from the Danish ealdorman, who administered a shire or province for the King. The title was introduced to Britain by Canute in the 11th Century. An Earl’s title is normally taken from the Earldom he has been granted although this is not always the case. For instance, the Earl of March was not named after a city or county whereas the Earl of Burlington is named after the town of Burlington, his Earldom.
The wife of an Earl is a Lady, his eldest son is a Viscount, his other sons are The Honourable and his daughters are Ladies.
An Earl is styled Right Honourable and is addressed by the King or Queen as Our Right Trusty And Entirely Beloved Cousin.