The word 凉快 (liángkuai) is a compound adjective formed through the semantic combination of its two constituent morphemes: 凉 (liáng), meaning "cool" in terms of temperature, and 快 (kuai), which in this context extends beyond its usual meaning of "fast" to convey a sense of "refreshed," "pleasant," or "at ease." This structure follows a common pattern in Chinese where two near-synonymous or complementary adjectives are joined to create a single, more vivid or nuanced concept. Thus, 凉快 does not merely mean "cool," but more specifically describes a comfortably and refreshingly cool sensation, often providing relief from heat.