By Cheonmyeongdang practitioners — updated October 2026
Jia Wood (甲木) is Yang Wood — the upright tree that grows by reaching skyward through structure, principle, and clear-cut leadership. Yi Wood (乙木) is Yin Wood — the vine or flowering plant that grows by adapting, weaving around obstacles, and leveraging relationships. Because Jia is Yang and Yi is Yin, the same Heavenly Stem produces opposite Ten Gods for each Day Master, which means their ideal careers, favorable elements, and life strategies differ substantially despite sharing the Wood element.
Your Day Master is the Heavenly Stem of your Day Pillar — the third column in your Four Pillars (BaZi) chart, determined by the exact solar date of your birth. If that stem is 甲, you are Jia Wood. If it is 乙, you are Yi Wood. The Day Pillar is calculated using the solar calendar (not the lunar calendar), and each 60-year cycle contains six Jia Wood years and six Yi Wood years alternating with the twelve Earthly Branches.
In Korean Saju (사주), Jia Wood is 갑목 (甲木) and Yi Wood is 을목 (乙木). The underlying system is identical; only the romanisation differs.
This is the most important distinction between Jia and Yi Wood. Because polarity flips every Ten God calculation, the same stem means something completely different in each chart. The table below shows the correct Ten God for every Heavenly Stem as it appears in a Jia Wood chart versus a Yi Wood chart.
| Heavenly Stem | Jia Wood 甲 Ten God | Yi Wood 乙 Ten God |
|---|---|---|
| Jia 甲 (Yang Wood) | Friend 新胡 Bi Jian | Rob Wealth 劫责 Jie Cai |
| Yi 乙 (Yin Wood) | Rob Wealth 劫责 Jie Cai | Friend 新胡 Bi Jian |
| Bing 丙 (Yang Fire) | Eating God 馉神 Shi Shen | Hurting Officer 伤官 Shang Guan |
| Ding 丁 (Yin Fire) | Hurting Officer 伤官 Shang Guan | Eating God 馉神 Shi Shen |
| Wu 戊 (Yang Earth) | Indirect Wealth 仮责 Pian Cai | Direct Wealth 正责 Zheng Cai |
| Ji 己 (Yin Earth) | Direct Wealth 正责 Zheng Cai | Indirect Wealth 仮责 Pian Cai |
| Geng 庚 (Yang Metal) | Seven Killings 七杯 Qi Sha | Direct Officer 正官 Zheng Guan |
| Xin 辛 (Yin Metal) | Direct Officer 正官 Zheng Guan | Seven Killings 七杯 Qi Sha |
| Ren 壬 (Yang Water) | Indirect Resource 仮印 Pian Yin | Direct Resource 正印 Zheng Yin |
| Gui 癸 (Yin Water) | Direct Resource 正印 Zheng Yin | Indirect Resource 仮印 Pian Yin |
Key practical implications: Gui Water is Jia Wood’s Direct Resource (the most nourishing Water), while Ren Water is Yi Wood’s Direct Resource. Ji Earth is Jia’s Direct Wealth, while Wu Earth is Yi’s Direct Wealth. Xin Metal governs Yi Wood through the pressure of Seven Killings, where Geng Metal does the same for Jia — a complete reversal of which Metal is friendly or threatening.
Jia Wood and Yi Wood each form a different Heavenly Stem Combination (天干合), which can transform or neutralise the Day Master’s Wood energy under the right chart conditions:
Whether these combinations actually transform depends on the Earthly Branches, seasonal strength, and other stems in the chart. A single stem combination never guarantees transformation without broader chart support.
Jia Wood wealth (Ji Earth = Direct Wealth; Wu Earth = Indirect Wealth) is best accumulated through stable, structure-backed positions where integrity is rewarded over time. Jia Wood people who chase shortcuts often find their gains unstable. Yi Wood wealth (Wu Earth = Direct Wealth; Ji Earth = Indirect Wealth) can arrive through diverse income streams and opportunistic ventures — Yi Wood people are often better positioned for portfolio careers or entrepreneurial side paths alongside a main role.
In BaZi, the spouse star for a male Day Master is the Wealth star, and for a female Day Master it is the Officer/Killings star. This means:
| Element | Effect on Jia Wood | Effect on Yi Wood |
|---|---|---|
| Water (Water nourishes Wood) | Gui Water (Direct Resource) is most beneficial; Ren Water is supportive but less targeted | Ren Water (Direct Resource) is most beneficial; Gui Water supportive |
| Fire (Wood produces Fire) | Bing Fire = Eating God (creative output, self-expression — generally good) | Ding Fire = Eating God (same positive effect for Yi) |
| Earth (Wood controls Earth) | Ji Earth = Direct Wealth; Wu Earth = Indirect Wealth. Beneficial when Wood is strong enough to control it | Wu Earth = Direct Wealth; Ji Earth = Indirect Wealth. Same logic applies |
| Metal (Metal controls Wood) | Xin Metal = Direct Officer (manageable authority); Geng Metal = Seven Killings (pressure/threat if uncontrolled) | Geng Metal = Direct Officer (institutional authority); Xin Metal = Seven Killings (pressure/threat if uncontrolled) |
| Wood (same element) | More Wood = more competition; beneficial only when Day Master is weak | Same: strengthens when weak, creates rivalry when strong |
Both Wood Day Masters are strengthened by being born in Spring (Tiger month = February, Rabbit month = March in the solar calendar) and weakened by Autumn (Monkey and Rooster months, peak Metal season). A Jia or Yi Wood born in Autumn requires strong Water or Fire in the chart to compensate.
| Axis | Jia Wood 甲 | Yi Wood 乙 |
|---|---|---|
| Polarity | Yang (陽) | Yin (陰) |
| Symbol | Tall tree, oak, timber, pillar | Vine, flower, grass, shrub |
| Growth mode | Vertical, linear, upward | Lateral, adaptive, weaving |
| Leadership style | Front-facing authority, hierarchy | Influence through rapport and timing |
| Stem combination | 甲己合 (with Ji Earth / Direct Wealth) | 乙庚合 (with Geng Metal / Direct Officer) |
| Direct Wealth star | Ji Earth 己 | Wu Earth 戊 |
| Direct Officer star | Xin Metal 辛 | Geng Metal 庚 |
| Seven Killings star | Geng Metal 庚 | Xin Metal 辛 |
| Direct Resource star | Gui Water 癸 | Ren Water 壬 |
| Eating God star | Bing Fire 丙 | Ding Fire 丁 |
| Season of strength | Spring (Tiger, Rabbit months) | Spring; also resilient in Summer |
| Career archetype | Executive, architect, judge, educator | Consultant, designer, communicator, counsellor |
| Relationship tendency | Loyal, protective, can be controlling | Warm, socially adept, can over-accommodate |
Your Day Master is only one of eight characters. The Month Branch (season), Hour Pillar, and current Luck Pillar can completely change which elements are favorable for your specific chart.
Jia Wood (甲木) is Yang Wood — the upright tree — direct, principled, and hierarchy-oriented. Yi Wood (乙木) is Yin Wood — the vine or flower — flexible, socially adept, and relationship-driven. Because Jia is Yang and Yi is Yin, the same Heavenly Stem generates opposite Ten Gods for each, meaning their ideal career environments, favorable elements, and life strategies differ substantially despite sharing the Wood element.
Jia Wood thrives in roles that reward long-term vision, structural authority, and integrity: management, law, civil service, education, architecture, and engineering. Because Geng Metal is Jia’s Seven Killings — a pressure star — Jia Wood benefits from the discipline of clear hierarchy and rule-bound environments where that pressure is channelled productively.
Yi Wood excels in roles that reward adaptability, communication, and relationship capital: public relations, counselling, design, sales, consulting, and content creation. Because Geng Metal is Yi’s Direct Officer — a status star — Yi Wood can advance through institutional roles when it builds the right alliances, rather than by challenging authority directly.
No — and this is the critical practitioner distinction. Because Jia is Yang and Yi is Yin, the same Heavenly Stem produces opposite Ten Gods. For example: Geng Metal is Seven Killings (七殺) for Jia Wood but Direct Officer (正官) for Yi Wood; Ding Fire is Hurting Officer for Jia but Eating God for Yi; Ji Earth is Direct Wealth for Jia but Indirect Wealth for Yi. Every favorable element analysis must be calculated separately for each Day Master.
Jia Wood (甲) combines with Ji Earth (己) in the 甲己合 stem combination, which can transform toward Earth under the right seasonal conditions. Yi Wood (乙) combines with Geng Metal (庚) in the 乙庚合 stem combination, which can transform toward Metal. These are entirely different combining partners — Jia combines with its Wealth star while Yi combines with its Officer star — which produces different psychological tendencies and chart vulnerabilities for each Day Master.