Excess of Yin and Yang refers to the pathological changes caused by excess of one side of Yin or Yang, which restricts the other side too much. Excess of yang leads to heat. At this time, excess of yang and pathogenic factors show signs of excess heat in clinic. When yin is abundant, it is cold. At this time, yin and evil are abundant, showing signs of excess cold.
the decline of yin and yang refers to the pathological changes of yin and yang below the normal level. Yang deficiency is cold, and at this time, qi deficiency is positive, showing deficiency-cold syndrome. Yin deficiency leads to heat. At this time, yin fluid in human body is deficient, showing deficiency-heat syndrome.
On the whole, the excess of Yin and Yang is the excess of excess, while the deficiency of Yin and Yang is the manifestation of deficiency of righteousness.