clean-air

The compound 'clean-air' is a modern English formation, directly combining two native and borrowed elements with transparent meanings. 'Clean' originates from a Proto-Germanic root conveying purity and freedom from adulteration, while 'air' descends from the ancient Greek term for the lower atmosphere. The compound's logic is entirely literal, describing air that is free from pollutants. Its evolution into a fixed adjective, especially in political and environmental contexts ('clean-air legislation'), represents a 20th-century semantic specialization where the literal quality becomes an advocated standard or goal.

Structure: clean (free from dirt) + air (the invisible gaseous substance) clean: From Old English clǣne (pure, clean, clear), of Germanic origin; related to Dutch klein and German klein. In this compound, it functions as an adjective modifying 'air'. air: From Old French air, from Latin āēr, from Greek aēr (air, atmosphere). In this compound, it functions as the noun being modified.