h₁óynos
“one, single, alone”one, single
PIE word for one. Gives Latin ūnus, English "one", "an", "alone", Greek oínē "ace on die".
Discussion
*h₁óynos is the Proto-Indo-European word for "one, alone, single." Unlike the higher numerals, "one" is built on a pronominal base, reflecting its dual function as both a number and an indefinite marker.
In Germanic, the word became Proto-Germanic *ainaz (with *oy > ai), yielding Gothic ains, Old English ān, and modern English "one." The same source gave "an," "a" (the indefinite article), "alone" (all-one), "any," "atone" (at-one), "none," and "only." German ein and Dutch een continue the form.
Latin ūnus "one" (from *oinos) is the source of a vast English vocabulary: "unit," "union," "unique," "universe" (turned into one), "uniform," "unify," "unanimous," and "unicorn." The prefix uni- is among the most productive in English.
Greek οἴνη (oínē) meant "the ace on a die" — literally "the one." The more common Greek word for one, εἷς (heîs), derives from a different root (*sem-).
Old Irish óen/aon "one" and Welsh un directly continue the PIE form in Celtic. The dual etymology of English "one" (native Germanic) and "unit" (Latin borrowing) from the same PIE source is a classic case of doublets.
Notes
Source of "union", "unit", "unique", "universe"
Related Roots
English Words from *h₁óynos
These modern English words descend from this root. Each page traces the full journey from PIE to present-day English.