one-seventh

The compound "one-seventh" is a transparent numerical construction in English, directly combining the cardinal number "one" with the ordinal form "seventh." The word "one" has a deep lineage tracing back to a fundamental Proto-Indo-European root for singularity. "Seventh" is built upon the ancient cardinal number "seven," also of Proto-Indo-European origin, with the addition of the ordinal suffix "-th," which grammaticalizes the concept of position in a sequence. The logic of the compound is purely arithmetic: it names a single unit from a set that has been divided into seven equal parts, making its modern meaning a direct and literal reflection of its constituent morphemes.

Structure: one (numeral) + seventh (ordinal number suffix) - one: From Old English 'ān', meaning the number 1. Its ultimate origin is Proto-Indo-European óynos, meaning "one, single". - seventh: From Old English 'seofoþa' (seventh), derived from 'seofon' (seven) + the ordinal suffix '-þa' (modern '-th'). 'Seven' originates from Proto-Indo-European septḿ̥.