Guest–host qi
How annual guest qi overlays fixed host qi for each six-step window. When both share the same element, they are “qi aligned” (同气) and the season’s character is amplified.
Guest qi is the moving atmospheric overlay assigned each year; host qi is the fixed six-step sequence. Their meeting — Ke-Zhu Jiaolin — describes the dominant climatic flavour of the current ~60-day step. TianJi computes the overlay deterministically for daily cards; this glossary entry explains the classical term only.
When people ask what “qi aligned” means: guest qi and host qi match in element for that step (qi resonance / 同气). See the guest-host alignment guide for the full explanation.