The Chinese word "不愠不火" is formed through a symmetrical structure where "不" (meaning "not") negates each of the two components: "愠" (meaning "angry" or "irritated") and "火" (here meaning "fiery" or "overly intense"). This creates the paired phrases "不愠" (not angry) and "不火" (not fiery), which are combined to convey a state of being neither emotionally agitated nor excessively heated, resulting in a term that describes moderate and composed behavior.