yin

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

yin and yang

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.