A civilisation is sometimes defined as a sophisticated culture characterized by five characteristics: (1) advanced cities, (2) specialized employees, (3) complex institutions, (4) record keeping, and (5) advanced technology. Although these traits are commonly associated with large urban populations, they also appear in smaller societies that lack modern amenities. Civilizations arise where there is sufficient population density to support a royal court, an army, and a bureaucracy. They require abundant natural resources to sustain their growth and technological innovation. Without access to these resources, a society would remain small and vulnerable.