Yin and Yang in TCM can be divided into two categories：abstract and concrete Yin and Yang. Concrete Yin and Yang can be measured， and so has certainty and decidability. When we say that kidney Yin and kidney Yang has observability in TCM， we don’t mean that there are some type of Yang essence or Yin essence in our body which can be detect by instruments. Attributes of an object can be divided into two categories：Yang attributes， which are relatively Yang on greater value， and Yin attributes， which are relatively Yin on greater value. Based on this understanding， We say that Yang deficiency is the lower value state of Yang attributes against normal state， Yang sufficiency is the greater value state of Yang attributes against normal state. Deficiency or sufficiency of Yin can be understood by analogy. Generally， An object which has n relatively independent attributes can be divided into 3n states， of which there is only one state and normal state.