‘循环’ (xún huán) literally combines ‘循’ (to follow, to trace) and ‘环’ (ring, circle, loop), together evoking the idea of moving along a closed path that repeats endlessly. As a noun, it means ‘cycle’ or ‘circulation’—referring to any recurring process or continuous flow, especially in natural, biological, or mechanical systems.

The word is widely used in scientific, ecological, and everyday contexts: the water cycle (水循环), blood circulation (血液循环), computer programming loops, and even social or economic patterns. It emphasizes repetition with continuity—not just one round trip, but an ongoing, self-sustaining pattern. While it can occasionally function as a verb (e.g., 循环播放), its primary and most frequent use is nominal, often modified by classifiers like ‘一个’ or adjectives like ‘自然的’ or ‘人工的’.