天干
ten heavenly stems — the visible layer
The chart is built from two alphabets. The first is the ten stems — 甲乙丙丁戊己庚辛壬癸 — the "heavenly" layer. 干 gān means trunk; the stems are the tree's main line, and the twelve branches (module 4) hang off them. Together they form the 干支 gān zhī system, older than the Shang dynasty oracle bones that first record it.
Each stem is a bundle of three facts: a phase (two stems per phase), a polarity (yang then yin, alternating), and an image (the traditional picture of how that phase-pair behaves). Ten stems, five pairs — each pair is one phase in its yang and yin register.
the ten stems in full
Notice the pattern: each yang stem is the phase at full display; each yin stem is the same phase turned inward. The sun and the candle are both fire; the mountain and the field are both earth. The distinction is register, not rank.
| stem | phase · polarity · image |
|---|---|
| 甲 jiǎ | 木 wood · yang · the sprouting tree — armor, the first, beginnings that break ground |
| 乙 yǐ | 木 wood · yin · the winding shoot — supple growth that finds the gap |
| 丙 bǐng | 火 fire · yang · the blazing sun — brilliance made visible, warmth for everyone |
| 丁 dīng | 火 fire · yin · the candle flame — steady, focused heat that lights one room well |
| 戊 wù | 土 earth · yang · the mountain — massive, defensive ground that does not move |
| 己 jǐ | 土 earth · yin · the field — soil that grows exactly what is planted in it |
| 庚 gēng | 金 metal · yang · the forged blade — harvest and renewal, the edge that clears |
| 辛 xīn | 金 metal · yin · the jewel — metal refined, sharp but precious |
| 壬 rén | 水 water · yang · the great river — carried, vast, moving toward the sea |
| 癸 guǐ | 水 water · yin · rain and dew — the gentle water that nourishes without flooding |
stem combinations — 五合 — 天干五合
Beyond the ten, the stems pair across the two polarities in five classical combinations: 甲己合 (wood-earth), 乙庚合 (wood-metal), 丙辛合 (fire-metal), 丁壬合 (fire-water), 戊癸合 (earth-water). The tradition reads each as a fusion that transforms into a phase — 甲己合化土, 乙庚合化金, 丙辛合化水, 丁壬合化木, 戊癸合化火. This is classic doctrine: an attraction across the cycle, a yang stem meeting its yin counterpart five places away.
Honest note: the app's engine computes branch interactions (module 8) and 十神 relations (module 7); stem combinations are taught here as doctrine and marked for a future engine release. The curriculum teaches the system; the engine computes the part of it that is pinned and verified — and we would rather under-compute than fake-compute.
the day master — 日主
One stem in the chart carries the reading: the day stem, called the 日主 day master. It is the traditional "you" — the lens every other character is read through (module 7 builds the whole 十神 system on this). Read it as a lens, not a label: the day master names the register your chart speaks in, not your final identity. In the app, the day pillar is ringed in the chart grid — you can always find the lens.