I Ching consists of 64 guas and 384 yaos. There are two special yaos in addition, so, 386 yaos in total. A gua or hexagram is composed of six yin and yang lines, arranged from the bottom to the top one by one (each line is called yao in Chinese). Yin (The symbol is broken line like 
, expressed 0 here in this Home Page) represents feminine, weakness, capacity, woman, the earth, even number and the receiver of energy. Yang (The symbol is solid line like 
, expressed 1 here in this Home Page) represents masculine, strength, development, man, the heaven, odd number and the donor of energy.
All the 64 guas and the yaos of each gua have the interpretation or the decision. A gua may relate to another through the change of one or more lines, or yaos. The methodology of the change will be explained in detail later. One of the "ritual numbers", 6, 7, 8 or 9 is assigned by the divination procedure to each of the six yaos in the gua. 6 and 8 are assigned to yin, 7 and 9 to yang. Why 6 and 8 to yin? Because they are broken or divided into two, which means weak, or yin. The 6 and 9 have tendency to change to 7 and 8 respectively. 7 and 8 have tendency to remain the same, or stable. This is much like a quantum leap in quantum mechanics. 7 and 8 are ground states.
In general, it is the lines that change that yield specific interpretation in I Ching. So, in I Ching, Yin is named Six and Yang is Nine. In a gua, for instance, the first or bottom yao is called "Initial Six" or "Initial Nine" corresponding to yin or yang. The second is "Second Six" or "Second Nine", and so forth. The sixth one is called "Top". Because it is up-most in a gua.
With three yaos piled up one by one, called eight little guas or trigrams, the I Ching categorizes them according to the scene or character of nature, members in a typical family. The eight trigrams and the meanings are shown in the following tables respectively.
