A phase of the Wu Xing means very little on its own. What gives it content is its position in two cycles that run through all five, and Wood is a good place to see how they work.
The generating cycle, sheng, runs Wood to Fire to Earth to Metal to Water and back to Wood. Each phase produces the next: wood feeds fire, and water in its turn feeds wood. The overcoming cycle, ke, runs Wood to Earth to Water to Fire to Metal and back to Wood, skipping one place each step, so that each phase restrains the one it reaches. Wood breaks up earth, and metal cuts wood. Every phase therefore stands in four relations at once: it is produced, it produces, it restrains, and it is restrained. That four-way position, not any list of attributes, is what the phase actually is.
In the classical Chinese medical literature Wood is the phase of the liver and the gall bladder, of the eyes, of the sinews, of spring, of the east, of the colour green, of the sour flavour and of anger among the emotions. These are recorded correspondences within that system. They are not claims about physiology in the modern sense and nothing here is guidance for any use.
The same five-phase logic organised argument well outside medicine. Dynastic legitimacy was contested in these terms, with each house claiming the phase that succeeded its predecessor's, and the choice between the generating and the overcoming sequence for that purpose was itself a political question.
Sources Science and Civilisation in China, Volume 2: History of Scientific ThoughtJoseph Needham with Huangdi Neijing (The Yellow Emperor's Inner Classic)Traditionally attributed to Huangdi; actual authorship unknown