If people's horoscope is regarded as a big tree, heavenly stems are equivalent to the trunk of the big tree, earthly branches are equivalent to roots, and the strength of heavenly stems and five elements hidden in earthy branches is equivalent to water and nutrients. If a tree wants to have strong vitality, its root system must be developed, so that it can penetrate into every corner and absorb more water and nutrients. Similarly, if the heavenly stems want to be strong, they must have their own roots in the underground branches. The more roots, the greater the strength of the five elements. We call this root system the same root.
The root system of the heavenly stems in the earthly branches must have the same attributes with it, for example, the heavenly stems are wood, and the five hidden elements in the earthly branches are also wood, so it can be regarded as the root system of the heavenly stems and called its "similar five elements", while the earthy branches with this "similar five elements" are called "tonggen".
For example, the eight characters: Ganbingwu, in which the Japanese stem is "Ren" and the Japanese branch and the monthly branch have "Ren", which can be called the roots of the Japanese stem.
Second, the role of Tonggen in the eight characters
Whether the heavenly stems have roots or not is the most important factor to judge the rise and fall of the five elements in the eight-character life. No matter how many heavenly stems are exposed, if there is no root in the soil, the power of heavenly stems is not very strong. The rise and fall of heavenly stems mainly depends on the number of roots in the soil. There is a saying in the ancient book: "Excess of qi in the middle leads to the root, which can be used to rob the two." It can be seen that the power of roots can not be ignored.