The eight principles refer to yin and yang, exterior and interior, cold and heat as well as deficiency and excess. The manifestations of diseases, though complicated, can be generalized into certain patterns in the light of the eight principles.

八纲是指阴阳、表里、寒热、虚实。疾病的表现尽管及其复杂，但基本上都可以用八纲加以归纳。