"Xíng" () of "wǔxíng" () means moving; a planet is called a 'moving star' ( "xíngxīng") in Chinese. Wǔxíng originally refers to the five major planets (Jupiter, Saturn, Mercury, Mars, Venus) that create five dimensions of earth life. "Wǔxíng" is also widely 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 "xíng" are "primarily concerned with process and change," hence the common translation as "phases" or "agents". By the same token, "Mù" 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.