Cool

Cool is an adjective describing a temperature that is lower than warm but not cold; it can describe air, water, or surfaces that feel moderately cold. It can also describe objects that feel cool to the touch. In meteorology, cool characterizes climates or seasons with comfortable temperatures, though exact ranges vary by context.

Etymology: The word derives from Old English col meaning cold; related to Dutch koel and German kühl. In English, "cool" exists since Middle English, and its figurative senses—calmness, poise, and later fashion—developed in the 20th century in slang.

Science sense: In physics and engineering, cooling refers to removing heat from a system by conduction, convection, radiation, or evaporation. The process continues until thermal equilibrium with the surroundings is reached. Common techniques include refrigeration, fans, heat exchangers, and liquid cooling.

Cultural use: In everyday language, "cool" designates something or someone as attractive, desirable, or socially approved. Phrases like "keep your cool" refer to maintaining composure, while "cool factor" and "coolness" describe style or authenticity.

Global and linguistic note: The term has been widely adopted across languages and cultures, often retaining both literal temperature and figurative meanings, with variations in nuance.