Si (巳) Earthly Branch: the Snake, Yin Fire, and What It Means in Your Bazi Chart

The Snake is the quietest predator in the zodiac, and Si (巳) matches that reputation perfectly. It looks like a straightforward Fire branch on the surface, but crack it open and you find Metal being born inside the flames, with Earth settling underneath. Three hidden elements coexist in what seems like an impossible arrangement — making Si one of the most internally complex characters in the entire [[Earthly Branch]] cycle.

一 What Si (巳) Actually Is

Si 巳 is the sixth of the twelve Earthly Branches, carrying Yin Fire as its native element. Its animal symbol is the Snake, and its polarity is [[Yin]] — inward, strategic, contained. For the underlying framework, see Earthly Branches in Bazi: The Twelve Characters and Their Hidden Stems.

Beneath the surface, Si holds three [[Hidden Stems]]:

Fire, Metal, and Earth sharing a single branch. What makes this especially striking is the relationship between the first two: Fire melts Metal, yet Metal is born here. In the twelve-stage growth cycle, Si is the 长生 (cháng shēng) position of Metal — meaning this is where Metal energy first comes into existence. The paradox is real: the element that destroys Metal is also the place where Metal begins its life. Fire provides the forge, and Metal emerges from the heat.

Seasonally, Si governs the fourth solar month, running from 立夏 (Lǐxià, Start of Summer) to 芒种 (Mángzhòng, Grain in Ear) — roughly early May to early June. This is early summer: the sun climbs higher each day, warmth builds steadily, and the landscape shifts from spring green to the fuller heat ahead. The Snake hour runs from 09:00 to 11:00, the stretch of morning when the sun is gaining authority but has not yet reached its peak.

The classical image captures it: the morning sun gaining strength, heat building with elegance and purpose, not yet the blazing noon. The Snake coils quietly, radiating warmth while concealing the Metal and Earth within. Fire is the obvious element, but the hidden 庚 Metal and 戊 Earth give Si a depth that pure Fire branches like Wu (午) simply do not have. Si is Fire at its most sophisticated — controlled, layered, and carrying the seeds of something entirely different inside.

二 Where to Find Si in Your Chart

Your [[Four Pillars]] chart is a grid of four columns — Year, Month, Day, and Hour — each with a [[Heavenly Stem]] on top and an Earthly Branch on the bottom. Si can appear in the branch row of any of those four positions:

• Year branch — You were born in a Snake year (e.g., 1989, 2001, 2013, 2025).
• Month branch — You were born during the fourth solar month, from the 立夏 Lǐxià solar term to just before 芒种 Mángzhòng. This falls roughly in May on the Western calendar, though the exact dates shift by a day or two each year. As a month branch, Si signals birth during early summer — a time when heat is building, energy is rising, and the chart carries that ascending quality.
• Day branch — The day you were born falls on one of the sixty [[Jiazi]] cycle days that pairs with 巳. This repeats every twelve days and has nothing to do with the calendar month.
• Hour branch — You were born between 09:00 and 11:00 in [[true solar time]] (adjusted for your birth longitude, not the clock on the wall).

Because Si participates in several powerful branch combinations — harmonies, clashes, punishments — its position relative to neighboring branches shapes the reading significantly. A Si next to Shen (申) behaves very differently from a Si next to Hai (亥).

三 How to Read Si

Once you know where Si appears, the next step is figuring out what it means for your specific chart. That depends on the pillar position, the relationship between Si's hidden stems and your [[Day Master]], and which other branches surround it. The method is easier to compare with Chen (辰) Earthly Branch: the Dragon, Yang Earth, and What It Means in Your Bazi Chart.

Three hidden stems, three ten god relationships

Si delivers three [[Ten God]] relationships at once. Take a 甲 Jiǎ (Yang Wood) Day Master as an example:

This is where Si becomes genuinely fascinating for chart reading. The dominant energy is Eating God (creative output at 1.0), but hiding beneath it is Seven Killings (pressure and control at 0.5), with Indirect Wealth (acquisition at 0.3) rounding out the picture. On the surface, Si looks like pure output — talent, expression, creativity flowing from the Day Master. But the Metal being born inside that Fire means the controlling element is growing within the output. Pressure emerges from within one's own production. The thing you create eventually disciplines you.

The Metal birthplace paradox

Si's role as Metal's 长生 (birth) position is the key to reading this branch correctly. In a chart dominated by Fire, the hidden 庚 at 0.5 contributes only moderate Metal influence. But when Si participates in certain branch combinations — especially the Si-You-Chou (巳酉丑) [[three harmony]] — that nascent Metal gets drawn out and amplified dramatically. The Metal born inside the flames matures into a full Metal bureau. Whether Si functions primarily as Fire or primarily as a Metal incubator depends entirely on what else appears in the chart.

Pillar position matters

The same set of ten gods reads differently depending on which pillar Si occupies:

• Year branch — Ancestry, grandparents, early childhood environment. Si here colors the family background with its Fire energy and hidden complexity — warmth on the surface, with Metal discipline and Earth resources embedded underneath.
• Month branch — Career, social standing, the world you operate in during adulthood. Si as month branch carries a literal meaning: birth during early summer, when energy is rising and heat is building. The chart inherits that ascending, purposeful quality.
• Day branch — The self, the spouse, the inner world. Si in the day branch sits directly beneath your Day Master and often describes the dynamics of your closest relationship. With three elements hidden inside, including both output and control, the relationship has layers.
• Hour branch — Children, aspirations, the later phase of life. Si here points toward creative output and hidden strength that may define the later years, fitting for a branch where Metal is born — something new emerging from established heat.

Si is also one of the four 驿马 ([[Travel Star]]) branches, signaling movement and change for charts with certain day branches. When it appears as a travel star, Si's Fire-and-hidden-Metal nature suggests purposeful journeys — travel that forges something new rather than idle wandering.

四 When Si Plays Out Differently

A branch never operates in isolation. Si is involved in several dramatic interactions that can reshape its meaning entirely. Here are five key scenarios, each verifiable in the calculator. This point connects directly with Wu (午) Earthly Branch: the Horse, Yang Fire, and What It Means in Your Bazi Chart.

1. Si-Shen (巳申) six harmony — Fire and Metal transform toward Water

When Si and Shen 申 appear in adjacent pillars, they form one of the six [[six harmony]] pairs. This combination transforms toward Water — one of the most counterintuitive results in branch theory. Fire (Si) and Metal (Shen) come together and produce something neither of them naturally represents. The classical explanation is that Metal born in Si (长生) meets Metal at its peak in Shen (临官), and their union generates Water through the Metal-produces-Water productive cycle. The practical effect: Si's Fire nature is redirected away from heat and toward flow. Snake meets Monkey, and what they create together surprises everyone.

2. Si-You-Chou (巳酉丑) three harmony — the Metal bureau

When Si 巳, You 酉, and Chou 丑 all appear among the four branch positions, they form the [[three harmony]] Metal bureau. This is where Si's hidden 庚 takes center stage. The Metal that was merely born inside Si now gets fully drawn out and amplified, joining forces with You's dominant 辛 Metal and Chou's hidden 辛. Si's Fire identity recedes, and its Metal incubator function takes over. The forge has done its work: what was being tempered inside the flames now stands on its own as part of a complete Metal framework.

3. Si-Hai (巳亥) clash — Fire versus Water in direct opposition

Si (Snake) and Hai 亥 (Pig) sit directly opposite each other in the branch circle, forming a [[six clash]]. This is Fire versus Water in its purest form. Si's 丙 Fire tries to evaporate Hai's 壬 Water; Hai's Water tries to extinguish Si's Fire. Which element prevails depends on seasonal strength and which visible stems sit above each branch. If the chart is born in a Fire-strong season, Si may hold its ground. In a Water-strong season, Hai overwhelms. Either way, the collision is intense and tends to disrupt whatever pillar Si occupies.

4. Yin-Si-Shen (寅巳申) punishment — the punishment of ingratitude

When Yin 寅, Si 巳, and Shen 申 all appear together, they form the 无恩之刑 — the [[punishment]] of ingratitude. This is one of the classical three-branch punishment patterns. Fire is born in Yin (寅), matures in Si (巳), and meets Metal's seat in Shen (申). The triangle creates a cycle of mutual undermining: each branch contributes to the next but receives no gratitude in return. The classical reading suggests relationships where help given is not acknowledged, or where the cycle of give-and-take breaks down into one-directional drain.

5. Si-Yin (巳寅) harm — Wood feeds Fire but is drained

When Si and Yin 寅 appear together, they form a [[harm]] relationship. Wood (Yin) naturally feeds Fire (Si) through the productive cycle, so on the surface this looks like a nourishing connection. But the harm means the feeding becomes draining rather than generative. Yin's Wood pours energy into Si's Fire without receiving anything back. The result is a quiet exhaustion — not a dramatic break, but a persistent one-way flow where the source runs dry while the fire keeps burning. It shows up as situations where giving becomes depleting rather than fulfilling.

五 Real Charts

Chart A — Si as month branch with Si-Shen six harmony

Si sits in the month branch, and the year branch Shen (申) forms the Si-Shen six harmony (巳申合水). This is one of the most counterintuitive harmonies in the system: Fire (Si) and Metal (Shen) combine and transform toward Water, pulling both branches away from their native elements. For the 甲 Jiǎ Wood Day Master, that redirection matters enormously.

Look at the Metal pressure first. Seven Killings totals 2.5 — the heaviest single ten god in the chart — fed by the visible 庚 in the year stem (1.0), Shen's hidden 庚 (1.0), and Si's own hidden 庚 (0.5). That is substantial controlling force bearing down on the Day Master. But the six harmony softens this by pulling some of that Metal-Fire energy toward Water. Water is Resource for Wood, meaning the harmony converts pressure into nourishment. The force that could crush the Day Master is being partially redirected into the element that feeds it.

The day branch Xu (戌) adds a layer of Indirect Wealth from its dominant 戊 Earth (1.0), giving the Day Master territory to conquer. The hour branch Zi (子) provides Direct Resource — a clean source of Water support arriving in the latest part of the chart. Two 甲 stems (day and hour) mean the Day Master has a companion: the hour's Friend adds solidarity without competition. The chart reads as a Day Master under significant Metal pressure, with a harmony mechanism quietly converting that pressure into sustenance.

Chart B — Si-Hai clash with Fire-Water tension

Si in the month branch faces a direct clash with Hai (亥) in the year branch — the 巳亥冲, Fire versus Water in head-on collision. The visible stems mirror the clash perfectly: 丁 (Yin Fire) sits above Si while 癸 (Yin Water) sits above Hai, each stem reinforcing its branch's native element. This is a chart where the clash is fully supported from above, making it particularly active and hard to ignore.

But that is not the only clash here. The day branch Shen (申) and the hour branch Yin (寅) form another opposition — the 寅申冲, Wood versus Metal. Two active clashes running in parallel through the four pillars, pulling the chart in opposing directions at every level. Fire fights Water across the year-month axis; Metal fights Wood across the day-hour axis.

For the 甲 Jiǎ Wood Day Master, the Fire output is the strongest force in the chart. Eating God totals 2.5, fed by the visible 丙 in the hour stem (1.0), Si's hidden 丙 (1.0), and Yin's hidden 丙 (0.5). This suggests enormous creative and expressive energy — the Day Master produces output prolifically, possibly because of the constant tension rather than despite it. The twin clashes keep everything in motion: nothing settles, nothing stagnates, and the Day Master channels that restless energy into production. The Friend total of 1.5 (from Hai's hidden 甲 and Yin's hidden 甲) provides enough Wood support to keep the Day Master standing, while the Indirect Resource total of 1.5 ensures a steady flow of Water nourishment even as Hai's Water is under siege from Si's Fire.

六 How Common Si Is

Across all 518,400 possible Four Pillars combinations, Si (巳) appears as the day branch in 43,200 charts (8.3%), as the month branch in another 43,200 (8.3%), and in at least one of the four branch positions in approximately 152,375 charts (29.4%). These numbers are identical for every earthly branch — the sixty Jiazi cycle distributes the twelve branches evenly, so no branch is rarer or more common than any other.

What does vary is how Si interacts with its neighbors. Because Si carries Metal in its birth stage and participates in some of the most dramatic combinations — the Si-Shen six harmony toward Water, the Si-You-Chou Metal three harmony, the Si-Hai Fire-Water clash, and the Yin-Si-Shen punishment of ingratitude — charts containing Si tend to have at least one active and often surprising branch interaction. The Snake is never as simple as it looks.