The meaning of Yin and Yang can be a difficult concept to understand because it is symbolic and relative rather than concrete and absolute. Therefore, it is not easy to define, and it is best explained in examples and metaphors.
Yin Embodies the Ideas of Substance, Moisture and Coolness
Yin is often thought of as the feminine aspect of nature. It is described as cool and damp, material and dense. The shady side of the mountain, the moon, darkness and passivity are Yin qualities. While each individual has aspects of both Yin and Yang in his or her constitution, a person with a predominantly Yin nature might have low energy, be pale, delicate or thin, have a soft voice, low blood pressure and a tendency to feel cold.
In the body, Yin is represented by blood, sweat, tears, and all forms of moisture, as well as the material part of the body such as the flesh and muscles. The Yin, or Zang, organs (liver, heart, spleen, lungs and kidneys) are the solid organs whose function is primarily to hold or store substances.
In TCM diagnosis, internal, chronic, cold and deficient patterns are Yin. An individual with excess Yin would display symptoms of dampness, which might include edema, mucus, diarrhea, copious urine and lack of thirst. Conversely, Yin deficiency manifests as symptoms of dryness. Dry skin and hair, burning dry eyes, scanty urination, constipation, lack of perspiration and fatigue are all signs of deficient Yin. If the Yin deficiency is extreme, signs of heat may appear, such as night sweats, a burning sensation in the chest, palms and soles of the feet, low fever and restlessness. This is known as “false Yang” because the Yin becomes so depleted that it cannot balance the Yang, so the Yang becomes predominant.
Yang Embodies the Ideas of Activity, Dryness and Heat
Yang is described as masculine, warm and dry, active and light. The sunny side of the mountain, the sun, heat and activity are Yang qualities. Someone with a predominantly Yang constitution might be energetic and aggressive, have a loud voice, high blood pressure, and a tendency to feel warm.
In the body, Yang is represented by metabolic activity, including digestion and movement, such as circulation of blood. The Yang, or Fu, organs (gall bladder, small and large intestines, stomach and urinary bladder) are the hollow organs whose primary function is to transform substances and transport them throughout the body.
Yang patterns in TCM are external, acute, hot and excess. Excess Yang manifests as extreme heat signs, such as high fever, red face and eyes, irritability, agitation, thirst and scanty, dark colored urine. Deficient Yang appears as fatigue, feeling cold, copious urine, loose stools and edema. Symptoms of deficient Yang may resemble those of excess Yin, but they differ in their underlying cause. Deficient Yang is caused by a lack of heat, so that the body is unable to transform, metabolize and stay warm, resulting in feelings of coldness and a buildup of fluids, while excess Yin is an overabundance of dampness.
The Relationship Between Yin and Yang
In their book, Between Heaven and Earth, Harriet Beinfield and Efrem Korngold define Yin as substance, and Yang as activity. Using the example of a candle to illustrate the relationship between Yin and Yang, the solid, heavy wax is the Yin component, paired with the insubstantial, hot, bright flame representing the Yang. Beinfield and Korngold explain that the interaction between Yin and Yang “reflects the interaction of matter and energy. Their dependence on each other renders them inseparable. Yang … transforms. Yin provides the material basis for the transforming power of Yang.”
Yin and Yang are interdependent and cannot exist in isolation. Each balances the other and contributes to the harmony of the body as a whole.