As opposed to youxing (有形 corporeal), wuxing (无形) literally means “incorporeal” or “formless.” The incorporeal cannot be described using such formal measurements as size, length, and weight, thereby they are lacking the formal confines that separate one thing from another. There are several types of incorporeal things. Qi, as one example, cannot be seen but can be felt. The way (dao), as another, can neither be seen nor be felt and therefore cannot be designated by a name. In ancient times, it was generally recognized that the incorporeal serve as the nature of or origin for the generation and changing of the corporeal.

The way of heaven is void and incorporeal. Given that it is impossible to exhaust the void or to collide with the incorporeal, the way of heaven can remain unchanged when circulating among all things. (Guanzi)

Taixu, or the great void, is formless; it is the original state of qi. Whether qi coalesces or dissipates, it is just a temporary form of taixu. (Zhang Zai:Enlightenment Through Confucian Teachings)