1. 每个别卦都是由上下两个经卦组成，分别叫做上卦和下卦，或者外卦和内卦。64卦有一定的先后次序，卦序中包含有深刻的哲理。 Each of the 64 symbolic hexagrams is made up of two parts, named upper trigrams and lower trigrams or outer trigrams and inner trigrams.