with regard to Chinese philosophy, the two converse, but complementary aspects of the basic standards overseeing the world. Initially, the words referenced the shady and sunny sides of a hill. The yin and yang are the two forces or standards which can be observed at work within all phenomena. At times, one is dominant over the other, and all things eventually return to their converses.
YIN AND YANG: "The yin and yang is a popular symbol of good and evil. "