Yin and yang began as the shady and sunny sides of a hill
The famous pair of opposites is not a battle between good and evil. In Chinese thought yin and yang are complementary forces that feed and sustain each other, shaping everything from seasons to kung fu. Even the characters carry a landscape inside them: a hill, a cloud, and the sun's rays.
In Chinese cosmology the universe grows out of a primal chaos of qi, material energy, which organises itself into cycles of yin and yang. Yin is receptive, contracting and passive; yang is active, expansive and outward-pushing. Behind both lies taiji, the Supreme Ultimate, a state of undivided potential before any duality, contrasted with the older idea of wuji, meaning without pole. From the play of qi come the ten thousand things between Heaven and Earth, humans among them.
Pairs like light and dark, fire and water, or expanding and contracting are read as visible expressions of this single principle. It underpins branches of classical Chinese science and philosophy, serves as a core guide in traditional Chinese medicine, appears in the I Ching and the Huangdi Neijing, and organises martial and movement arts including tai chi, baguazhang and qigong.
Philosophers did not all agree on its moral weight. Taoist metaphysics treats good and bad as matters of perception, so yin and yang form one indivisible whole. Confucian ethics, especially in the work of Dong Zhongshu around the 2nd century BC, attached a moral dimension to the pair. Among some Ahom people, descendants of the Dai minority whose tradition began in Yunnan, a duality of the self called han and pu draws on the same idea.
Both characters share a component meaning mound or hill. Yin adds an element for cloud, and yang contains the sun and a sign for sunbeams. Yin, spoken in the level first tone, can mean cloudy, shady, feminine, the moon or hidden; yang, in the rising second tone, can mean sunny, male or positive, even in the electrical sense. Linguist Axel Schuessler proposes Sino-Tibetan roots for both, comparing yin with a Burmese word for overcast and yang with Burmese and Lepcha words for brightness.
Source: Yin and yang
