The paper first defines the terms used to describe the types of authority in a terrorist entity. These terms are "strategic control," which refers to the ability to define the top-level goals and aims of the group; "operational control," which is the ability to control or influence the activities and operations performed in pursuit of the organization's goals; and "tactical control," which is the ability to control or influence the specific activities an individual or component of the organization performs. These terms that define types of authority are then used to distinguish a terrorist entity as a "tightly-coupled group," in which commanders or opinion leaders within the group exert strategic, operational, and tactical control; a "coupled network," which is marked by the loosening of the control and influence that commanders or opinion leaders can exert over other components; and a "loosely coupled movement," which manifests a further loosening of the control and influence linkages within an organization. The next major section of the paper categorizes and defines the boundaries of real-world terrorist organizations, with attention to al Qaeda. It discusses the definition of the internal and external boundaries of terrorist organizations, a loosely coupled movement as boundary, the coupled network as boundary, and the tightly coupled group as boundary. The paper advises that defining a terrorist entity or its various components by the strength of command-and-control linkages is important in tailoring counterterrorist measures to how operations are designed and implemented. 71 notes