循環

The term describes a process where something moves in a continuous loop, returning to its origin. While it is frequently used in medical or biological contexts to describe blood flow, its application extends far beyond biology to include environmental systems and abstract socio-economic cycles.

In a physical sense, it refers to the movement of fluids or gases, such as air circulation in a room or the water cycle in nature. In these cases, the focus is on the continuous, rhythmic movement that maintains a state of balance or health.

In a metaphorical or systemic sense, it describes the flow of resources, money, or events. A particularly common usage is the contrast between a virtuous cycle (好循環 - kōjunkan) and a vicious cycle (悪循環 - akujunkan). A virtuous cycle refers to a chain of positive events that reinforce each other, while a vicious cycle describes a downward spiral where one problem leads to another, making the situation worse.

Compared to the verb 巡る (meguru), which can describe a simple movement around something or a change in turns, 循環 emphasizes the systemic nature of the loop—the idea that the process is a closed, repeating circuit essential for the functioning of the whole system.