The term has three meanings. First, it indicates the original essence of all things.
It is another name for dao (way). It is also referred to as taiyi (the supreme one).
Second, it refers to the state of chaos before the separation of heaven and
earth. The one was divided and transformed into heaven and earth. All things in
heaven and on earth were produced from this Chaotic entity. Third, it indicates
the unity of things, as opposed to "many" or "two." The idea is to emphasize the
unity among things which are different or opposite.