Letters patent (always in the plural) are a type of
legal instrument in the form of a published written order issued by a
monarch,
president, or other head of state, generally granting an office, right,
monopoly, title, or status to a person or
corporation. Letters patent can be used for the creation of
corporations or government offices, or for the granting of city status or a
coat of arms. Letters patent are issued for the appointment of representatives of the Crown, such as
Governors and
Governors-General of
Commonwealth realms, as well as appointing a
Royal Commission. In the United Kingdom they are also issued for the creation of peers of the realm. A particular form of letters patent has evolved into the modern
patent (referred to as a utility patent or
design patent in
United States patent law) granting exclusive rights in an
invention (or a design in the case of a
design patent). Clearly in this case it is essential that the written grant should be in the form of a public document so other inventors can consult it to avoid infringement and also to understand how to "practice" the invention, i.e., put it into practical use.