Heavenly stems and earthly branches
Stems are visible signals, branches are contextual roots, and together they form the coordinate system of a chart.
Stems are visible; branches are rooted
Stems appear directly and often show visible expression, identity, and relationships. Branches act like environment and roots, containing hidden stems that add depth beyond the visible eight characters.
The month branch is usually pivotal
The month branch represents birth season and strongly affects element strength. The same wood day master born in spring versus autumn can behave very differently.