In brief
The chapter’s title term: the four seasonal qi, and the regimen that answers to each. ‘Regulating the spirit with the four qi’ (四氣調神) means ordering one’s inner life by the season rather than by appetite.
氣 in the plural and with a number: not one vapour but four, each with its own character — spring issues and spreads, summer flowers, autumn levels and gathers, winter closes and stores.
The verb the title pairs with it is 調, to tune or bring into accord. What is being tuned is 神, the spirit. The chapter’s claim is that the inner life is not self-governing: it has to be set against the season.
Passages where the term does real work, with the original, pinyin and English on the same line.
Every rendering below is a decision about which reader is being addressed. There is no neutral option.