One character out of eight
Of the eight characters in a chart, one represents you directly: the Heavenly Stem of your day pillar, called the Day Master (일간, ilgan). Every other character is read in relation to it. The same character that means wealth for a Fire person means career for a Metal person, so nothing in a chart can be interpreted until the Day Master is known.
The ten natures
There are ten Heavenly Stems, and each is one of the five elements in either a yang (expansive) or yin (receptive) form. Traditional teaching gives each a picture from nature, and the pictures are surprisingly useful.
Wood: 甲 Gap is the Tall Tree — upright, principled, grows straight toward a goal. 乙 Eul is the Flower and Vine — adaptable, patient, wins by climbing rather than pushing.
Fire: 丙 Byeong is the Sun — warm, open, shines on everyone and needs to be seen. 丁 Jeong is the Lantern — a small light that lasts all night, illuminating one thing deeply.
Earth: 戊 Mu is the Mountain — steady, reliable, slow to move. 己 Gi is the Field — nurturing, practical, works best with a plan.
Metal: 庚 Gyeong is Rock and Raw Metal — direct, decisive, refined by pressure. 辛 Sin is the Jewel — polished, precise, shines when recognized.
Water: 壬 Im is the Ocean — vast, restless, values freedom over comfort. 癸 Gye is Rain and Dew — intuitive, subtle, soaks in quietly and changes everything.
Yang and yin are not gender
Yang stems act outward and yin stems act inward, but both appear in everyone's chart regardless of gender. A yang Day Master tends to initiate and declare; a yin Day Master tends to observe, adapt and finish. Neither is stronger. A Lantern can outlast a Sun; a Vine can cover a Mountain.
Strength: does your chart feed you?
A Day Master is 'strong' when the surrounding characters share its element or produce it, and 'weak' when they drain or control it. Strength is not good or bad — it changes what helps you. A strong Fire person benefits from Water and Metal, which give the fire something to work on. A weak Fire person benefits from Wood, which feeds it. This is why the same advice cannot apply to everyone with the same Day Master.