From a spatial perspective

three yin and three yang in Inner Canon of Yellow Emporor（《黄帝内经》）is explained by the different space regions in human body

which are closely related to the name of twelve meridians.There are two postures of the viewer

who is called"Saint"

to confirm the regions of three yin and three yang

southfacing posture and supine posture. According to the known positions of twelve meridians

it could be understood the positions of three yin and three yang described in the chapter of Separation and Combination of Yin and Yang in Plain Questions（《素问·阴阳离合论篇》）. We established the probationary polar coordinate system and a combination of half of Cartesian coordinate system and half of polar coordinate system which is called "Saint coordinate system"

to explain the position of three yin and three yang by mathematical linguistics. It was discovered that Saint coordinate system could well illustrate the original meaning in Inner Canon of Yellow Emporor. And the two coordinate systems above are helpful to affirm the yin-yang’s property of twelve channel water

which are described in the chapter of The Relationship between Rivers and Channels in Miraculous Pivot（《灵枢·经水》）.