Yang was initially symbolized by the warmer, southern side of the mountain, a sunny bank, later the mountain as a whole. Subsequently Yang represented everything including light and bright day, summer and sun. Also dryness, air (wind) and fire were assigned to Yang, as well as increasingly warm days of spring, the warmer season’s flourishing and revival of nature, all that is active, creative, invigorating, expanding, shiny, external. Yang corresponds to the hard and masculine. Yang manifests itself in odd numbers and is represented by a solid line, for example | or also
When doing the divination with yarrow stalks, fifty dried stalks are selected from a bundle and taken in the left hand. Then one yarrow stalk is put away. The remaining 49 yarrow stalks are divided into two piles and, taking four yarrow stalks from each pile, are counted according to a complicated system until the result is either 2 or 3. This process is repeated three times and the sum is added up. The values 6 and 8 represent a broken line (yin) and 7 and 9 a solid line (yang). This process is repeated six times until the hexagram is complete. The values 6 and 9 are regarded as changing lines, i.e. they change into their respective opposite: 6 (Yin) becomes 7 (Yang), 9 (Yang) becomes 8 (Yin). This transforms the original hexagram into another of the 64 hexagrams.
Yin originally referred to the colder north side of a mountain, the shaded river bank or the darker, cooler south side of a valley. Later on Yin was associated with the idea of days with cool weather and overcast skies, with shadows and all that is dark, cool and humid, with water and earth, night and winter. Yin qualities correspond to winter, the passive, hidden, astringent, dull, interior. Yin is associated with the soft and feminine. Within the I Ching Yin is represented by even numbers and a dashed line such as | ¦ or als
Yin und Yang are central concepts of Chinese philosophy, especially Daoism, which applies this dualism to everything. According to Daoism Yin and Yang are fundamental aspects of reality, simultaneouly interdependent and complementary to each other, rhythmically alternating during the course of life.