Wu Xing - the Five Phases or Elements
A further refinement of Yin/Yang are the Five Phases or Five Elements. Although not so ancient as the Yin/Yang concept, they have been a part of Chinese thought since at least 400 BC.
The Chinese term Xing is difficult to translate exactly. It gives the idea of walking, one step then another, the idea of progress, movement, a living process, a stage in a cycle.
It is commonly translated either as 'Element' which is perhaps a bit too static, or 'Phase', which lacks the idea of a particular quality. The problem is similar to deciding whether light is a particle or a wave.
The Five Phases are Wood, Fire, Earth, Metal and Water. Just as Yin/Yang represents a spinning unit of rest/activity, of dark/light, of inward and outward movement, so the Five Phases represent five different movements or aspects of energy, five energetic tendencies, five vibratory rates.
It may be easier to think of these in terms of the seasons. There arc two Yin seasons (Autumn and Winter) and two Yang seasons (Spring and Summer) and their qualities illustrate the aspects of the Phases they are associated with.