yinyang, Wade-Giles romanization yin-yang, Japanese in-yō, in Eastern thought, the two complementary forces that make up all aspects and phenomena of life. Yin is a symbol of earth, femaleness, darkness, passivity, and absorption. It is present in even numbers, in valleys and streams, and is represented by the tiger, the colour orange, and a broken line. Yang is conceived of as heaven, maleness, light, activity, and penetration.