There are three meanings to the term. 1) The five fundamental things or elements that make up all things. The Book of History was the first to define the five elements: metal, wood, water, fire, and earth. Each of these has its own properties and they interact in a generative or destructive relationship. 2) On a more abstract level, the term refers to the basic framework to understand the world. All things can be included in the realm of wuxing (五行) and their properties are explained or understood accordingly. 3) It refers to five kinds of moral behavior. Xunzi once criticized Zisi and Mencius for “creating wuxing on the basis of old theories.” Ancient bamboo slips unearthed from a grave at Guodian dating back to the State of Chu as well as inscribed silk texts from the Mawangdui Tomb of the Western Han Dynasty, all describe this wuxing as benevolence, righteousness, li (礼), wisdom, and the wisdom and character of a sage.
In heaven there are the sun, moon, and stars, while on earth there are the five elements: metal, wood, water, fire, and earth. (Zuo’s Commentary on The Spring and Autumn Annals)
The qi of heaven and that of earth merge into one; it evolves into yin and yang, the four seasons, and the five elements of metal, wood, water, fire, and earth. (Dong Zhongshu: Luxuriant Gems of The Spring and Autumn Annals)