In the British peerage, 'Lord' serves as both a formal rank and a generic form of address for those holding titles such as Baron, Viscount, Earl, or Marquess. While a Duke is addressed specifically by his rank, all other members of the peerage are collectively referred to as the 'Temporal Lords' within the House of Lords. The term encompasses those who hold their titles 'in tail male' by letters patent from the Crown, as well as 'Lords by Courtesy'—the eldest sons of high-ranking peers who use a secondary title without holding a legal seat in the upper house.
Heraldically and legally, the title implies a direct feudal relationship with the Sovereign. From the post-Conquest era through the development of the modern peerage, a Lord was characterized by his tenure of land 'in capite' (directly from the King) and his obligation to provide counsel and military service. In contemporary usage, it also includes Life Peers appointed under the Life Peerages Act 1958, who enjoy the rank for their lifetime without the inheritance of the title by their heirs.