letters patent (always in the plural) are a type of legal instrument in the form of a published written order issued by a monarch, or government. they are generally used in 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. they may be used 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. 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). this grants exclusive rights of an invention (or a design in the case of a design patent). 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. it is also important to understand how to "practice" the invention or put it into practical use.