Xiang (象) refers to a visible but formless image or figure. It approximately has four different meanings. First, it refers to a manifest shape of Dao. Laozi described Dao as “a semblance of the unsubstantial,” also called “the great semblance.” Second, it indicates a manifest shape of objects. Xiang is less concrete or fixed than an object with a shape. It often means celestial phenomena, namely, the movements of the sun, the moon, and the stars, and the occurrence of wind, thunder, clouds, and rain. Celestial phenomena are relative to earthly shapes. Third, it refers to human temperament, namely, the human spirit and mind, manifested in words, deeds, and attitude. Fourth, it refers to figures symbolizing or imitating all things in heaven and on earth. Ancient Chinese created many kinds of systems of xiang, through the observation and interpretation of which they elucidated the changes in the movements of nature and of society, and also their laws. Among them, the system of the hexagrams and figures of The Book of Changes is the most influential.
Above, Dao is not manifest, while lower down it is not obscure. It is ceaseless but cannot be described, and it then turns to nothingness. This is called the shape of the shapeless, and the semblance of the unsubstantial. Such a state is called indistinct. (Laozi)
In heaven it is semblance, and on earth it has concrete shape, and this demonstrates change of things. (The Book of Changes)
Hexagrams and trigrams described in The Book of Changes allowed sages to survey the secret of all things under heaven and determine what was fitting through simulation of the shapes of things. That is why they were called semblances. (The Book of Changes)