The word 城市 (chéngshì, meaning "city") is formed through a conceptual fusion of two ancient and fundamental ideas of human settlement: the first character, 城, originally referred to a defensive wall or a fortified area, emphasizing the structural and protective aspect of a place, while the second character, 市, denoted a marketplace or a center of trade and commerce, representing the economic and social hub. Together, they logically combine to describe a single, complex entity where the fortified place and the commercial center are no longer separate but integrated, evolving into the modern concept of a city as a major, densely populated urban center encompassing both physical infrastructure and vibrant human activity.