Wu Xing (五行), the Five Phases, is a classification system in traditional Chinese medicine that describes cycles of generation and restraint among five functional categories: wood, fire, earth, metal, and water. The standard translation “Five Elements” is misleading — xing means “movement” or “phase,” not “element.” These aren’t substances in the Greek sense but patterns of transformation (Kaptchuk, 2000).
Each phase corresponds to a cluster of associations: an organ-function system, a season, an emotion, a sensory organ, a taste, a color, a direction. Wood corresponds to the Liver system, spring, anger, the eyes, sourness. Fire corresponds to the Heart system, summer, joy, the tongue, bitterness. Earth corresponds to the Spleen system, late summer, overthinking, the mouth, sweetness. Metal corresponds to the Lung system, autumn, grief, the nose, pungency. Water corresponds to the Kidney system, winter, fear, the ears, saltiness.
The phases relate through two cycles. The generating cycle (sheng 生) describes how each phase supports the next: wood feeds fire, fire creates earth (ash), earth yields metal (ore), metal enriches water (minerals), water nourishes wood. The controlling cycle (ke 克) describes how each phase restrains another: wood parts earth (roots), earth dams water, water extinguishes fire, fire melts metal, metal cuts wood. Health depends on both cycles operating smoothly. When the generating cycle falters, a downstream phase weakens. When the controlling cycle fails, a phase dominates unchecked.
Nathan Sivin observed that the Five Phases operate as a system of correspondences rather than causes (Sivin, 1987). A practitioner who identifies a “wood overacting on earth” pattern — irritability, digestive disturbance, a wiry pulse — isn’t claiming that an entity called “wood” is attacking an entity called “earth.” They’re describing a recognizable clinical configuration and using the Five Phases vocabulary to locate it within a system of relationships that suggests both the mechanism and the treatment principle.
Related terms
- Yin and Yang — the complementary polarity framework that operates alongside the Five Phases
- Qi — the circulating force whose behavior the Five Phases classify
- San Bao — the Three Treasures, another diagnostic axis
- Traditional Chinese Medicine — the medical tradition that uses this framework