A term that means different things in different contexts. Basically the world we experience is Dao — what is Naturally So.

Dao is the path that conforms to the way the universe works. It is

responsible for the motion of the cosmic structure; indeed, it is more powerful than the cosmos itself.

— Deborah Lynn Porter: From Deluge to Discourse (1996:65)

Dao is “here and now.” Wu-wei is how you accord with Dao.

Daoism proposes that the natural order of things does not need to be helped, fixed or saved, and the way to be in harmony within oneself and with the external world is to welcome it and go with it, not against it.

If you fight the natural flow … you will only cause yourself and others trouble.

… Daoism advises you to seek to know and accord yourself with the Dao … so that you’re in the flow instead of fighting it. You are perfectly free to fight it, or course, or perfectly free to go with it.

— John David Hoag

Traditional feng shui is about you finding out how to “go with the flow,” rather than forcing the flow to give you what you want!

The meaning of wu wei was, so far as the early proto-scientific Taoist philosophers were concerned, ‘refraining from activity contrary to Nature’, i.e., from insisting on going against the grain of things, from trying to make materials perform functions for which they are unsuitable, from exerting force in human affairs when the man of insight could see that it would be doomed to failure, and that subtler methods of persuasion, or simply letting things alone to take their own course, would bring about the desired result.”

— Joseph Needham: Science and Civilization in China (Volume 2)

Dao is related to chaos,

signified by the chaotic unintelligibility of the Milky Way.

— Deborah Lynn Porter: From Deluge to Discourse (1996:66)

Nature, society, and humanity form a trinity. All things possess their own te or virtue (like destiny). When te is not opposed it also follows what is Naturally So.