The ten heavenly stems
Every pillar has a character on top. That's its stem. There are ten of them, the heavenly stems (天干, ). Each one is an element, in either its Yang or its Yin way. The tradition gives each a picture from nature, and the pictures do most of the explaining.
Wood
- 甲 , Yang Wood: a tree. It grows straight up, gives shade and holds steady in the wind.
- 乙 , Yin Wood: a vine. It bends, climbs and finds a way around walls. Some books picture it as a flower.
Fire
- 丙 , Yang Fire: the sun. It warms everything at once and can be seen from far away.
- 丁 , Yin Fire: a candle. A small, steady light for the page in front of you.
Earth
- 戊 , Yang Earth: a mountain. Solid, slow to move, a landmark others steer by.
- 己 , Yin Earth: garden soil. Soft and fertile. It helps other things grow.
Metal
- 庚 , Yang Metal: worked metal. A sword or an axe fresh from the forge. Strong, direct, made for hard work.
- 辛 , Yin Metal: a jewel. Fine and precise. It shines when it's cared for.
Water
- 壬 Rén, Yang Water: a river. Always moving, always opening its own path.
- 癸 , Yin Water: rain. Rain, dew and mist. Quiet, it nourishes without making noise.
Big and small of the same thing
Each element comes in two sizes, more or less. The Yang stem is the big, open version: the tree, the sun, the mountain. The Yin stem is the smaller, closer one: the vine, the candle, the garden. You'd look after a tree and a vine differently, even though both are Wood. In the same way, two people with Fire as their core element can feel very different if one is the sun and the other a candle.
The ten in order
The stems always run in the same order: 甲 乙 丙 丁 戊 己 庚 辛 壬 癸. Wood, Fire, Earth, Metal, Water, each one Yang and then Yin. Years follow this order too. A year ending in 4 has 甲 as its stem, a year ending in 5 has 乙, and so on around. 2026, for example, has 丙, Yang Fire. (Keep in mind the BaZi year starts around February 4, not on January 1.)
Where the stems sit in your chart
Your chart has four stems, one per pillar. The one in your Day pillar is special: it's your Day Master, you inside the chart. The other three are read by how they get along with it, and that's what the ten roles describe. A Fire stem in your Month pillar might be Support for one person and Pressure for another. It depends on whose chart it sits in.
Stems also come from outside. Every decade, year, month and day has a stem of its own. On the Today tab, the top character of the day's arch is the day's stem, and the themes underneath come from how it meets your Day Master.
Branches carry stems too, tucked inside them. They're the same ten characters, called hidden stems. When you tap a pillar on the Chart tab, you'll see them under "Hidden stems", each with its role.
Stems that pull together, and stems that push
The tradition pairs some stems as partners: 甲 with 己, 乙 with 庚, 丙 with 辛, 丁 with 壬, and 戊 with 癸. When two partners meet, it's read as a pull toward each other, a close bond. A few others are set in tension: 甲 and 庚, 乙 and 辛, 丙 and 壬, 丁 and 癸. When you look at two people together, the app points these out between their charts.
In plain words
A stem is an element with a personality. Once you know its picture, you can read a lot from it. A river doesn't stand still, a mountain doesn't rush, and a candle does its best work up close.