In Chinese philosophy, Yin and Yang are generalized descriptions for two primal opposing but complementary cosmic forces that are believed to be present in all non-static objects and processes in the universe. Together, Yin and Yang create a unity, a complete whole. This paradox is the cornerstone of most branches of Chinese philosophy, and it is used extensively in Traditional Chinese Medicine.

The Taijitu (above), is the symbol which traditionally representing the opposing but complementary forces of Yin and Yang.

Yin

Yin is the dark element: it is passive, dark, feminine, downward-seeking, and corresponds to the night. Examples of Yin include shady places, north facing slopes (of mountains), south banks (of rivers), and cloudy / overcast days. Yin is often symbolized by water and earth. In the human body, Yin organs include:

• Heart,
• Kidney,
• Liver,
• Lung,
• Pericardium,
• Spleen

Yang

Yang is the bright element: it is active, light, masculine, upward-seeking, and corresponds to the daytime. Examples of Yang include sunny places, south facing slopes (of mountains), north banks (of rivers), and sunny days. Yang is often symbolized by fire and air. In the human body, Yang organs include:

• Gall bladder,
• Large intestine,
• Small intestine,
• Urinary bladder,
• Stomach,
• San Jiao - which is described by Chinese Medicine as the passage of heat and fluid throughout the body.

Yin (dark) and Yang (light) are descriptions of complementary opposites rather than absolutes. All forces of nature are seen as having Yin and Yang states, and the two are in a constant state of flux.

Under the Yin-Yang Theory, diagnoses rely on understanding of each organ's function and recognizing global patterns and symptoms of dysfunction and imbalance in the patient so that insight can be gained into the illness affecting the patient.