Jing means"go through" 0r "a path".They are the main trunks,thick and large.They run longitudinally and are deep level distributed within the body.They include the twelve regular meridians.The eight extra meridians and the twelve divergent meridians.

Luo means "something that connects"or "a net".They are branches of the meridians.They run transversely and are distributed superficially and crisscross and net the whole body.Thev include the fifteen collaterals and the minute collaterals and the superficial collaterals.

The theory of meridians-collaterals is theoretical doctrine that analyses the course and distribution of physiological function and pathological changes of the meridian-collaterals of the human body and their relationship between with the Zang-Fu organs.It is an important component in the basic theory of traditional Chinese medicine and the core of theory underlying acupuncture and moxibustion.It permeates physiology,pathology,diagnostic theories and treatment principles in Chinese medicine together with the theory of Yin-Yang and the five elements and the theory of Zang-Fu.It forms commonly the theoretical basis of Chinese medicine.