yin and yang

noun (used with a singular or plural verb)

1. (in Chinese philosophy and religion) two principles, one negative, dark, and feminine (yin), and one positive, bright, and masculine (yang), whose interaction influences the destinies of creatures and things.

noun

1. two complementary principles of Chinese philosophy: Yin is negative, dark, and feminine, Yang positive, bright, and masculine. Their interaction is thought to maintain the harmony of the universe and to influence everything within it

Two forces in the universe, according to a Chinese theory: yin is the passive, negative force, and yang the active, positive force. According to this theory, wise people will detect these forces in the seasons, in their food, and so on, and will regulate their lives accordingly.