Heavenly Stems — Tian Gan (天干)

The ten stems

Role in Liuyao (Najia system)

In the Najia system developed by Jing Fang during the Han dynasty, each of the eight trigrams is assigned a heavenly stem. Yang trigrams (Qian, Kan, Gen, Zhen) use yang stems; yin trigrams (Kun, Dui, Li, Xun) use yin stems. The stem determines the elemental character of the lines within that trigram's position in a hexagram.

For example, the trigram Qian (Heaven) is assigned the stems Jia (甲) for its inner lines and Ren (壬) for its outer lines. This means lines in the Qian position carry Wood (Jia) or Water (Ren) elemental associations through the stem, which then combines with the earthly branch to determine the full elemental identity of each line.

Practical significance

For most Liuyao readings, the heavenly stem layer is handled automatically by the casting system. What matters practically is the resulting elemental assignment of each line — whether it is Wood, Fire, Earth, Metal, or Water — and how that element interacts with the day and month of the reading.

Understanding stems becomes more important when studying the theoretical foundations of Liuyao or when working with traditional texts that reference stem assignments directly. For beginners, the Five Elements page provides a more accessible entry point into the same underlying system.