The Wu Xing, (五行 wŭ xíng) also known as the Five Elements, Five Phases, the Five Agents, the Five Movements, Five Processes, and the Five Steps/Stages, is a fivefold conceptual scheme that many traditional Chinese fields used to explain a wide array of phenomena, from cosmic cycles to the interaction between internal organs, and from the succession of political regimes to the properties of medicinal drugs. The "Five Phases" are Wood (木 mù), Fire (火 huǒ), Earth (土 tǔ), Metal (金 jīn), and Water (水 shuǐ). This order of presentation is known as the "mutual generation" (xiangsheng 相生) sequence. In the order of "mutual conquest" (xiangsheng 相勝) or "mutual overcoming" (xiangke相剋), they are Wood, Earth, Water, Fire, and Metal.
"Wu Xing" is often translated as Five Elements and this is used extensively by many including practitioners of Five Element acupuncture. This translation arose by false analogy with the Western system of the four elements. Whereas the classical Greek elements were concerned with substances or natural qualities, the Chinese xing are "primarily concerned with process and change," hence the common translation as "phases" or "agents." By the same token, Mu is thought of as "Tree" rather than "Wood". The word 'element' is thus used within the context of Chinese medicine with a different meaning to its usual meaning. Evolution of language in this way is not without precedent. It should be recognized that the word 'phase', although commonly preferred, is not perfect. 'Phase' is a better translation for the five 'seasons' (五運 wŭ yùn) mentioned below, and so 'agents' or 'processes' might be preferred for the primary term xing. Manfred Porkert attempts to resolve this by using 'Evolutive Phase' for 五行 wŭ xíng and 'Circuit Phase' for 五運 wŭ yùn, but these terms are unwieldy. In some ways arguing for one one term over another is pointless because any single word is probably inadequate for translation of what is a concept.
Some of the Mawangdui Silk Texts (no later than 168 BC) also present the Wu Xing as "five virtues" or types of activities. Within Chinese medicine texts the Wu Xing are also referred to as Wu Yun (五運 wŭ yùn) or a combination of the two characters (Wu Xing-Yun) these emphasise the correspondence of five elements to five 'seasons' (four seasons plus one). Another tradition refers to the wu xing as wu de 五德, the Five Virtues (zh:五德終始說).
The system of five phases was used for describing interactions and relationships between phenomena. After it came to maturity in the second or first century BCE during the Han dynasty, this device was employed in many fields of early Chinese thought, including seemingly disparate fields such as geomancy or Feng shui, astrology, traditional Chinese medicine, music, military strategy and martial arts. The system is still used as a reference in some forms of complementary and alternative medicine and martial arts.
Although it is usually translated as "element", the Chinese word xing literally means something like "changing states of being", "permutations" or "metamorphoses of being". In fact Sinologists cannot agree on one single translation. The Chinese elements were seen as ever changing and moving—one translation of wu xing is simply "the five changes".
The Wu Xing are chiefly an ancient mnemonic device for systems with five stages; hence the preferred translation of "movements", "phases" or "steps" over "elements."
In the bagua, metal is associated with the divination figure 兌 Duì (☱, the lake or marsh: 澤/泽 zé) and with 乾 Qián (☰, the sky or heavens: 天 tiān). Wood is associated with 巽 Xùn (☴, the wind: 風/风 fēng) and with 震 Zhèn (☳, the arousing/thunder: 雷 léi). In view of the durability of meteoric iron, metal came to be associated with the aether, which is sometimes conflated with Stoic pneuma, as both terms originally referred to air (the former being higher, brighter, more fiery or celestial and the latter being merely warmer, and thus vital or biogenetic). In Taoism, qi functions similarly to pneuma in terms of a prime matter (a basic principle of energetic transformation) that accounts for both biological and inanimate phenomena.
In Chinese philosophy the universe consists of heaven and earth. The five major planets are associated with and even named after the elements: Jupiter 木星 is Wood (木), Mars 火星 is Fire (火), Saturn 土星 is Earth (土), Venus 金星 is Metal (金), and Mercury 水星 is Water (水). Also, the Moon represents Yin (陰), and the Sun 太陽 represents Yang (陽). Yin, Yang, and the five elements are associated with themes in the I Ching, the oldest of Chinese classical texts which describes an ancient system of cosmology and philosophy. The five elements also play an important part in Chinese astrology and the Chinese form of geomancy known as Feng shui
The doctrine of five phases describes two cycles of balance, a generating or creation (生, shēng) cycle and an overcoming or destruction (克/剋, kè) cycle of interactions between the phases.