Yin

The oracle glyph of Yin shows two hands drawing an arrow — its root sense is "to draw forth": the bow drawn, and all things drawn up out of the soil. The Shuowen: "Yin — in the first month Yang qi stirs, rising up from the Yellow Springs." The whole character is tension before release.

Its image is the early-spring forest on a hill at dawn: towering Jia Wood (main qi), newborn Bing Fire (at its birth stage here), supporting Wu Earth (residual) — one branch, three stems, a complete ecosystem. None of the twelve carries a fuller landscape.

Yin computes as Jia Wood in interactions, but its true distinction is hosting Fire's birth: the life of Fire begins at Yin, which is why the Yin-Wu-Xu Fire frame takes Yin as its birth corner. Wood's upward drive plus Fire's first flame makes Yin an igniter — fast to start, fierce in momentum.

The Yin month contains Li Chun, the start of spring — and BaZi switches year pillars at Li Chun, not at Lunar New Year. This is among the most important casting rules: born before Li Chun, your zodiac and year pillar belong to the previous year.

Yin-Hai is one of the six combinations (into Wood) — Water feeding Wood, the most companionable of pairs. Yin-Wu-Xu forms the Fire frame with Yin as the birth corner. Yin versus Shen heads the four "birth-stage clashes": two igniters colliding, read as upheaval, travel, transport, relocation.

Yin-Si-Shen is the most famous punishment trio ("punishment of ingratitude"), tangling kindness into grievance when all three assemble. Every entry in Yin's relation dictionary carries the word "movement" — when Yin stirs, the scenery of a life changes acts.

Yin is Jia Wood's Lu throne — a Jia Day Master sitting on or drawing from Yin is a tree with its taproot, strong at the source. For Bing Fire, Yin is the birth-stage Resource palace; for Wu Earth, Seven Killings and birth stage share the same house — a layered, high-stakes configuration.

With Wu Earth hidden inside, Yin even moonlights in Earth structures. One Yin often works several jobs at once — Wood's throne, Fire's cradle, Earth's lodging — so its role can only be judged after fixing who the Day Master is.

The Yin hour (3–5 a.m.) was anciently "level dawn," the moment before light. Officials rose at Yin to make the Mao-hour roll call — the idiom "eating Mao's grain during Yin" (spending tomorrow's income today) is literally these two hours in sequence.

The Yin month is the first month: the Han calendar reform of 104 BCE fixed "first month built on Yin," and two millennia of the Chinese calendar followed. The entire Spring Festival system rests, at bottom, on this one character.