Void (Xún Kōng)
The two Earthly Branches in the same ten-day cycle as the pillar that lack a matching Heavenly Stem.
The sixty Jiazi are grouped into ten-day cycles. Each cycle contains ten Heavenly Stems and twelve Earthly Branches, so two branches in each cycle have no Heavenly Stem to pair with—these are the Xunkong (also called 'Kongwang') for that pillar.
For example, in the Jiazi cycle (Jiazi to Guiyou), the ten Heavenly Stems are used up, leaving Xu and Hai without a Heavenly Stem, so the Xunkong for the Jiazi cycle is Xu and Hai.
⚠️ Xunkong is determined based on the ten-day cycle of the Day Pillar. Different schools have varying views on whether it can be resolved.