In Chinese philosophy, the concept of yin yang (simplified Chinese: 阴阳; traditional Chinese: 陰陽; pinyin: yīnyáng, ‘um yang’ in Korean – often referred to in the west as yin and yang) is used to describe how seemingly opposing forces are interdependent in the natural world, giving rise to each other in turn. The concept lies at the heart of many branches of classical Chinese science and philosophy, as well as being a primary guideline of traditional Chinese medicine, and a central principle of several forms of martial arts and exercise, such as taijiquan, gung fu and qigong. Many natural dualities – e.g. dark and light, female and male, low and high – are cast in Chinese thought as yin yang.
The relationship between yin (simplified Chinese: 阴; traditional Chinese: 陰; pinyin: yīn) and yang (simplified Chinese: 阳; traditional Chinese: 陽; pinyin: yáng) is often described in terms of sunlight playing over a mountain and in the valley. Yin (literally the ‘shady place’ or ‘north slope’) is the dark area occluded by the mountain’s bulk, while yang (literally the ‘sunny place’ or ‘south slope’) is the brightly lit portion. As the sun moves across the sky, yin and yang gradually trade places with each other, revealing what was obscured and obscuring what was revealed. Yin is usually characterized as slow, soft, insubstantial, diffuse, cold, wet, and tranquil. It is generally associated with the feminine, birth and generation, and with the night. Yang, by contrast, is characterized as hard, fast, solid, dry, focused, hot, and aggressive. It is associated with masculinity and daytime.
Yin and yang are descriptions of complementary opposites rather than absolutes. Any yin/yang dichotomy can be viewed from another perspective. All forces in nature can be seen as having yin and yang states, and the two are in constant movement rather than held in absolute stasis.