In East Asian thought, the two complementary forces or principles that make up all aspects and phenomena of life. Yin is earth, female, dark, passive, and absorbing; it is present in even numbers and in valleys and streams and is represented by the tiger, the colour orange, and a broken line. Yang is heaven, male, light, active, and penetrating; it is present in odd numbers and mountains and is represented by the dragon, the colour azure, and an unbroken line. Together they express the interdependence of opposites.