one-way

The compound adjective 'one-way' is a transparent combination of two ancient English roots. 'One' descends from a core numeral in Proto-Indo-European, solidifying the concept of singularity. 'Way' originates from a root concerning movement and conveyance, evolving to denote a path or route. When combined in Modern English, the literal sense of "a single path" logically extends to describe systems, streets, or interactions that permit movement or action in only a single, non-reversible direction. This reflects a straightforward compounding process where the sum of the parts clearly conveys the restricted, unilateral nature of the modern term.

Structure: one (single) + way (path, direction) - one: From Old English 'ān', meaning "one, a single". Its ultimate origin is Proto-Indo-European óynos, meaning "one, single". - way: From Old English 'weg', meaning "road, path, course of travel". Its ultimate origin is Proto-Indo-European weǵʰ-, meaning "to bring, to transport".