Order is the architectural construct through which a unit defines constraints, permissions, and boundary conditions that govern how actions unfold. It establishes what is allowed, restricted, or required—making behavior legible, enforceable, and recoverable across agents, interfaces, and time. Without Order, systems become unstable: capabilities are invoked without constraint, rules fragment, and coordination collapses under ambiguity. In Purpose Driven Design, Order is not a layer of control but a structural grammar that enables bounded autonomy, reliable execution, and systemic alignment. This chapter establishes Order as the mechanism that transforms capability into governed behavior, ensuring coherence, accountability, and safe participation in complex sociotechnical systems.