In the context of the English Peerage, a Patent (strictly 'Letters Patent') is a legal instrument issued by the monarch under the Great Seal of the Realm. Unlike the more ancient 'Writ of Summons,' which created baronies by the act of sitting in Parliament, a Patent defines the specific rank, the precise line of succession—usually limited to 'heirs male of the body lawfully begotten'—and the territorial designation associated with the title. This method became the standard for creating new peerages during the 14th century, offering greater legal certainty regarding the inheritance of honors.
The document is issued 'open' (patens), meaning it is exposed to public view with the seal pendant at the bottom, signifying the Sovereign’s public declaration of the grant. Beyond the title itself, a Patent may also grant the right to bear specific heraldic augmentations or supporters. In modern practice, since the Life Peerages Act 1958, Patents are the exclusive mechanism for creating non-hereditary life sub-ranks, ensuring the recipient's seat in the House of Lords for the duration of their natural life without passing the honor to their descendants.