A physical thing, group of physical things, or an organization. This class is the super-type of all Entities (colored green) in the HL7 V3 Act-Role-Entity pattern. "A physical thing, group of physical things or an organization capable of participating in Acts while in a role. An entity is a physical object that has, had or will have existence. The only exception to this is Organization, which while not having a physical presence, fulfills the other characteristics of an Entity. Entity stipulates the thing itself, not the Roles it may play: the Role of Patient, e.g., is played by the Person Entity." HL7 RIM.