Stage 1 · Term 3 of 34
Heavenly Stem 天干
Tiān Gān
One of ten characters (甲乙丙丁戊己庚辛壬癸) expressing the five elements in yang and yin form. Stems are the visible, declared energies of a chart — what shows on the surface of each pillar.
In the classics
《滴天髓》 opens by characterising the ten stems' natures — 甲 the towering timber, 乙 the winding vine, 丙 the blazing sun, 丁 the lamp flame, and so on — images the whole tradition still teaches from.
In a chart
Stems are the declared layer of a chart: visible, active, quick to respond to what arrives in luck pillars and years. A stem with no root in the branches is classically called "floating" — loud but unsupported, promising more than the chart can bank. Stems also interact among themselves: the five combinations (甲己, 乙庚, 丙辛, 丁壬, 戊癸) can bind two stems' agendas together, another layer read at this level.
Worked example
甲 and 乙 are both wood, but 甲 is yang — assertive, structural, a pillar tree — while 乙 is yin — adaptive, winding, a climbing vine. Same element, opposite temperaments, and the classics never confuse the two.
Where beginners misread it
Treating all ten stems as five interchangeable element-pairs. Polarity is not a footnote: nearly every Ten God distinction in Stage 2 turns on it.
The classical rules here are public; the lineage method for applying them to a specific chart is taught, not read — see Yixin Academy's courses.
learnwithyixin.com/courses →What does Heavenly Stem mean in BaZi?
One of ten characters (甲乙丙丁戊己庚辛壬癸) expressing the five elements in yang and yin form. Stems are the visible, declared energies of a chart — what shows on the surface of each pillar.