《黄帝内经·素问·阴阳离合论》
但三者之间，不能各自为政，而是相互协调紧密联系着的，所以合起来称为一阴。
三经者不得相失也，搏而勿沉，名曰一阴。
However, the three meridians cannot operate independently, they coordinate and closely connect with each other. Thus, when combined, they are called one Yin.