The 10 Heavenly Stems (Tian Gan): Complete Guide

The 10 Heavenly Stems (Tian Gan 天干) are Jia (甲), Yi (乙), Bing (丙), Ding (丁), Wu (戊), Ji (己), Geng (庚), Xin (辛), Ren (壬), and Gui (癸). Each stem combines one of the Five Elements with yin or yang polarity: Jia and Yi are Wood, Bing and Ding are Fire, Wu and Ji are Earth, Geng and Xin are Metal, and Ren and Gui are Water. The first in each pair is yang and the second is yin. This creates 10 distinct visible expressions from 5 elements, a pattern described in San Ming Tong Hui.

The stems appear in the top position of each Bazi pillar. They represent what is visible, active, and expressed outwardly. The Earthly Branch below each stem holds the seasonal context and hidden stems that modify how the visible stem actually functions. Classical Bazi practice always reads the stem in relation to its branch, not in isolation.

The stem cycle has been used in the Chinese calendar for over 3,000 years. Oracle bone inscriptions from the Shang dynasty (c. 1600–1046 BCE) already used the ten stems to mark days. By the time Bazi developed its mature form in the Song dynasty, the stems had accumulated a rich layer of symbolic meaning that practitioners applied to personality, timing, and chart relationships.

Classical Bazi uses natural images to make each stem concrete. Jia (甲) is like a tall tree — upright, direct, and growth-oriented, with strong roots but limited flexibility. Yi (乙) is like vines and flowers — adaptable, persistent, and able to find support in unexpected places. Bing (丙) is like the sun — warm, generous, and visible to everyone, but unable to focus its light on one person. Ding (丁) is like candlelight — precise, intimate, and capable of sustained illumination in a small space.

Wu (戊) is like a mountain or dry earth — solid, reliable, and capable of holding great weight, but slow to change direction. Ji (己) is like cultivated soil — fertile, receptive, and able to nourish what is planted in it, but dependent on what it receives. Geng (庚) is like raw metal or an axe — strong, decisive, and capable of cutting through obstacles, but requiring refinement before it becomes truly useful. Xin (辛) is like jewelry or a refined blade — precise, beautiful, and sensitive to its environment.

Ren (壬) is like the ocean or a great river — vast, powerful, and capable of carrying enormous loads, but difficult to direct without strong banks. Gui (癸) is like mist, rain, or underground water — subtle, penetrating, and able to reach places that direct force cannot, but easily dispersed without containment. These images are not decorative — they are practical tools for reading how a Day Master expresses itself and what kind of environment supports or depletes it.

The Day Master is the stem of the day pillar. In Yuan Hai Zi Ping, the Day Master is the self — the reference point from which all other chart elements are interpreted. Every other stem and branch in the chart becomes a Ten God (a relationship role) based on how its element relates to the Day Master's element. A Jia Wood Day Master, for example, reads Bing Fire as its Output star, Geng Metal as its Authority star, and Ren Water as its Resource star.

This is why two people born in the same year with the same zodiac animal can have completely different Bazi readings: if one has a Jia Wood Day Master and the other has a Ren Water Day Master, the same surrounding elements play entirely different roles in each chart. The Day Master is not just one of eight characters — it is the lens through which all eight are read.

Identifying the Day Master is the first step in any Bazi reading. Once the Day Master is known, the reader can determine element strength, Ten Gods, useful and stressful elements, and how the luck cycle interacts with the natal chart. Without the Day Master as an anchor, the chart is a collection of symbols without a center.

Five stem combinations (天干合 tiān gān hé) describe pairs of stems that attract each other and can transform into a new element when conditions are right: Jia-Ji combine toward Earth, Yi-Geng combine toward Metal, Bing-Xin combine toward Water, Ding-Ren combine toward Wood, and Wu-Gui combine toward Fire. These combinations are significant because they can change the element count in a chart and alter how the Day Master functions.

A combination does not always transform. Classical practice checks whether the resulting element is supported by the season and surrounding branches before confirming the transformation. A Jia-Ji combination in a summer chart surrounded by Fire may not produce Earth, because the conditions for Earth to dominate are not present. This is why San Ming Tong Hui treats combinations as conditional rather than automatic.