乙丑 Day Pillar (Yi Chou): Na Yin and elements
What the Day Pillar shows
The 乙丑 (Yi Chou) Day Pillar pairs the Yin Wood Heavenly Stem with the Ox Earthly Branch. In a full chart this is the pillar readers use to locate the Day Master — the reference point from which other stems and branches are compared.
The Na Yin image
In the Na Yin tradition, the 乙丑 pair carries the image "Metal in the Sea" (海中金, Hai Zhong Jin). Na Yin is a poetic layer that assigns a combined image to each consecutive pair of pillars. It is a traditional vocabulary for noticing quality and texture, not a prediction.
How the stem and branch interact
The stem is Yin Wood (Wood) and the branch is associated with Earth; in this pairing, the stem element controls the branch element. Traditional readers describe this configuration as carrying productive tension.
A careful reading boundary
A Day Pillar is a calculated position inside a Four Pillars chart, not a verdict about a person. Read it with the Month Pillar, the visible elements, and the certainty of the birth record.