Trigrams
A trigram is a three-line figure. Two trigrams combine to form a six-line hexagram, so trigrams are one of the basic building blocks of I Ching and Liuyao structure.
Beginners do not need to memorize every traditional association at once. The practical point is that trigrams help readers notice structure: upper and lower tendencies, movement, and the shape of the situation.
The eight classic trigram names are Qian, Dui, Li, Zhen, Xun, Kan, Gen, Kun. Different traditions emphasize different symbolic correspondences, so Yarrow keeps the explanation modest and pattern-focused.
If you are reading a cast for the first time, it is usually better to understand how the two trigrams combine inside the hexagram than to chase every symbolic layer immediately.