• 循環じゅんかん — circulation; cycle
• 循環器じゅんかんき — circulatory system; cardiovascular system
• 循環型じゅんかんがた — recycling-based; circular (type)
• 循序じゅんじょ — order; proper sequence

With the movement radical 彳, 循 suggests “walking along a path” — not randomly, but in a followed route or cycle. That’s why it appears in words like 循環, meaning circulation or a repeating loop.