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BaZi (Four Pillars of Destiny) · Day Master 2 of 10

Yǐ 乙, yin Wood: the soft plant that binds to the tree

Yǐ 乙 is the second Heavenly Stem, yin Wood, and the day master of any BaZi chart whose day stem it is. The classical images make it grass, vine and flowering plant. The 滴天髓 grants it a strength its softness hides; the 三命通會 makes it wind in heaven and living wood on earth. As a day master it is rooted in 卯, 辰 and 未 and combines with 庚.

The ten Heavenly Stems in a row from 甲 to 癸, paired by phase, with 乙 Yǐ marked; below, the five phases on a circle, with arrows for the producing order and lines for the overcoming order, showing that Water produces Wood, Wood produces Fire, Wood overcomes Earth and Metal overcomes Wood. Wood 甲 Jiǎ 乙 Yǐ Fire 丙 Bǐng 丁 Dīng Earth 戊 Wù 己 Jǐ Metal 庚 Gēng 辛 Xīn Water 壬 Rén 癸 Guǐ 木 Wood 火 Fire 土 Earth 金 Metal 水 Water Yǐ · Wood Produced by Water Produces Fire Overcomes Earth Overcome by Metal produces overcomes
乙 among the ten stems, and Wood in the two classical orders: produced by Water, producing Fire, overcoming Earth, overcome by Metal.

Facts

Order
2 of 10, the second Heavenly Stem
Character
乙 Yǐ
Phase and polarity
Wood 木, yin 陰
Season of its phase
Spring
Produced by; produces
Water; Fire
Overcomes; overcome by
Earth; Metal
Rooted in (hidden in)
卯 Mǎo (main qi), 辰 Chén (residual qi), 未 Wèi (middle qi)
Comes into office (祿)
卯
Blade (陽刃)
None: in the Ziping rule only the yang stems have one
Born in (長生)
午, running the stages backward
Combines with
庚 Gēng, leaning to Metal
Clashes with
辛 Xīn
Our image
Vine and grass (EsoTerrier's modern image)

Meaning

The 滴天髓 gives each stem a verse of eight short lines. For 乙 it reads, in the 輯要 text:

乙木雖柔,刲羊解牛,懷丁抱丙,跨雞乘猴,虛濕之地,騎馬亦憂,籐蘿繫甲,可春可秋。

In our translation: Yǐ wood, soft as it is, can cut the goat and carve the ox. Holding 丁 and embracing 丙, it rides the rooster and mounts the monkey. On empty, damp ground even riding the horse is a worry. A vine tied to 甲, it does well in spring and in autumn.

The goat and the ox are the yin earth branches 未 and 丑, which it can master; the rooster and the monkey are the metal branches 酉 and 申, which it need not fear with fire beside it; the horse is 午, whose fire cannot help it on wet ground. Its best place is twined on the yang wood 甲, in any season.

The 三命通會 reads 乙 as wind in heaven and trees on earth: "living wood" (活木), soft wood that fears yang metal and the fall of autumn, and wants moist soil for its roots and living water for its leaves. Its sky image is the wind. The 窮通寶鑑 makes the 乙 of spring the orchid, the iris and the grass, unable to do without the sun (丙) or the rain (癸).

Our chart calls 乙 vine and grass: adaptable, creative, persistent and diplomatic, with leaning on others, and going round rather than through, as its cost. That is EsoTerrier's modern image, not the classical meaning; the texts' images stand beside it, each labelled.

In a chart

A 乙 day master has roots wherever 乙 is hidden in a branch: 卯 Mǎo (main qi), 辰 Chén (residual qi), 未 Wèi (middle qi). Its 祿, the branch where its qi comes into office (臨官), is 卯. In the Ziping rule only the yang stems have a blade, though the 三命通會 reports an older rule that gave 乙 one in 辰. It is born (長生) in 午 and, as a yin stem, runs the twelve stages backward from there, the rule every tool prints and the classics dispute; the stages are phases of its qi.

It combines with 庚 Gēng (天干五合), a pair the 三命通會 calls 仁義之合 (the match of benevolence and righteousness), leaning to Metal; it clashes with 辛 Xīn. Its own phase is strongest in spring.

To a 乙 day master the ten stems are: 甲 Rob Wealth (劫財); 乙 Friend (比肩); 丙 Hurting Officer (傷官); 丁 Eating God (食神); 戊 Direct Wealth (正財); 己 Indirect Wealth (偏財); 庚 Direct Officer (正官); 辛 Seven Killings (七殺); 壬 Direct Resource (正印); 癸 Indirect Resource (偏印). A second 乙 elsewhere in the chart is a Friend; the day stem itself is the Day Master and is not one of the Ten Gods.

What this page leaves out

The classical chapters on 乙 also say, in the idiom of their age, what such a chart means for rank, kin, marriage and fortune. We record that they do and repeat none of it. Nor do we say whether a 乙 day master is strong or weak, or which useful god it needs: the tradition weighs both, and EsoTerrier computes neither.

Correspondences

Each item with how it stands: “sourced” is in the work cited, “our construction” is EsoTerrier’s own, and “disputed” means the sources disagree.

Opening of the 滴天髓 verse
「乙木雖柔」 sourced
Sky image, 三命通會
Wind (風) sourced
In heaven and on earth, 三命通會
In heaven wind, on earth trees (在天為風,在地為樹) sourced
The first month, 窮通寶鑑
In spring 乙 is orchid, iris and grass; 丙 and 癸 are indispensable to it (三春乙木) sourced
Combination, 三命通會
With 庚: 仁義之合 (the match of benevolence and righteousness) sourced
Nobleman star (天乙貴人)
子 and 申; a symbolic star we do not chart yet sourced
Academic star (文昌)
午; a symbolic star we do not chart yet sourced
Blade under an older rule
辰, a rule the 三命通會 reports and the Ziping method drops disputed
Our image, traits and challenge
Vine and grass: adaptable, creative, persistent and diplomatic; its challenge: leaning on others, and going round rather than through our construction
Vine and grass as the classical meaning
A modern image; the classics give the ones above disputed
First meaning of the character
Uncertain; the stems are first attested as day names of the Shang week disputed

How the schools read it

滴天髓, the verse
Soft wood with a hidden strength, safe among metal when fire is near, at its best twined on 甲. Attributed to 京圖 of the Song or to Liu Bowen; one edition study dates the text mid-Ming or later.
任鐵樵, 滴天髓闡微 (after 1820)
Reads 跨鳳乘猴, the phoenix for the rooster; both stand for the branch 酉.
三命通會 (Ming)
Wind in heaven and trees on earth; living wood that wants moist soil and living water.
窮通寶鑑 (Qing)
Orchid, iris and grass in spring, needing both sun and rain.
Modern English teaching
The one-word image, vine and grass, a simplification of the classical images.
EsoTerrier
Shows vine and grass as its own image, labelled, beside the texts.

Claims about it

  • "Vine and grass" is the traditional meaning of 乙.

    disputed

    What the record shows: It is a modern teaching image, and ours on the chart. The 滴天髓 stresses the strength under the softness; the 三命通會 gives wind and living wood.

  • The day stem is itself a Ten God, the Friend (比肩).

    false

    What the record shows: A 乙 in another pillar is a Friend to a 乙 day master; the day stem itself is the reference point, labelled Day Master (日主) by every tool we surveyed.

  • 乙 runs the twelve stages backward, born (長生) in 午.

    disputed

    What the record shows: The 三命通會 says so and every tool prints it. The 滴天髓's older commentary already questions it, and 任鐵樵 rejects separate yin stages. We print the backward rule and label it.

  • A 乙 day master can be scored strong or weak, and its useful god computed.

    disputed

    What the record shows: The classics ground the useful god in at least four different ways. EsoTerrier computes neither the strength nor the useful god.

  • The classical chapters on 乙 tell a person's rank, marriage and length of life.

    told as lore

    What the record shows: The texts do make such pronouncements, in the idiom of their age. We take only their images and the logic of the phases.

Elsewhere on EsoTerrier

Sources

Primary texts (5)
  1. 淵海子平, the Ming compilation by 楊淙 of 徐大升's Song works. Chinese Wikisource transcription. zh.wikisource.org/wiki/淵海子平
  2. Wan Minying, 三命通會, 12 juan (Ming). Chinese Wikisource transcription. zh.wikisource.org/wiki/三命通會
  3. 滴天髓, the 滴天髓輯要 text with its older commentary. Chinese Wikisource. zh.wikisource.org/wiki/滴天髓
  4. 窮通寶鑑, the Qing edition by 余春台 of the 欄江網. Chinese Wikisource transcription. zh.wikisource.org/wiki/窮通寶鑑
  5. 任鐵樵, 滴天髓闡微 (after 1820), with the 原注. Chinese Wikisource transcription. zh.wikisource.org/wiki/滴天髓闡微
Studies and other sources (3)
  1. Na Hyeok-Jin and Kim Ki-Seung, "A Study on the Editions of Myeongri Original Text Jeokcheonsu (滴天髓)", Industry Promotion Research 6(3) (2021): 49 ff. doi.org/10.21186/IPR.2021.6.3.049
  2. Adam Smith, "The Chinese sexagenary cycle and the ritual foundations of the calendar", in John M. Steele (ed.), Calendars and Years II. Oxford: Oxbow, 2011 (read at abstract level).
  3. "Heavenly Stems", Wikipedia (orientation only). en.wikipedia.org/wiki/Heavenly_Stems
Our own research (4)
  1. EsoTerrier, BaZi and Luck Pillars research: conventions, naming and the tools surveyed, 9 to 13 October 2026.
  2. EsoTerrier, the BaZi data tables with their sources: hidden stems, Ten Gods, Na Yin, twelve stages, void branches, relations and symbolic stars.
  3. EsoTerrier calculation engine, the BaZi and Luck Pillars services and their documentation.
  4. EsoTerrier, the owner's decisions of 13 October 2026 on how the day-master pages show the images.

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By EsoTerrier. Written with AI assistance from our research and checked against its sources; last revised 19 October 2026. How we write these pages.

First published ; last revised . Corrections: support@esoterrier.com.

Chinese quotations are from public-domain texts as transcribed on Chinese Wikisource (CC BY-SA 4.0); the translations and readings are EsoTerrier's own.