h₂eyos
“metal, copper/bronze”metal/copper
PIE noun root for metal, especially copper or bronze. Source of Latin aes, English "ore," and metallurgical vocabulary.
Discussion
*h₂eyos is a Proto-Indo-European noun root meaning "metal," specifically "copper" or "bronze," reflecting the metallurgical knowledge of PIE speakers.
Latin aes "copper, bronze, money" is the central reflex (genitive aeris), yielding English era (from aera, originally a system of counting from a fixed date, connected to bronze coinage), and the chemical terms for copper-related elements. The shift from "metal" to "money" in Latin reflects the use of bronze as currency.
Sanskrit áyas- "metal, iron" shows a semantic shift from copper/bronze to iron as metallurgical technology advanced—the same word was reapplied to the new dominant metal. Avestan ayah- "metal" preserves the Iranian reflex. Gothic aiz "bronze" and Old English ār "bronze, copper" (whence English ore, originally meaning metal/bronze) continue the Germanic branch.
The wide attestation of this root across branches is significant for PIE chronology and homeland studies, as it places PIE speakers in a context of metal-working, consistent with a Chalcolithic or Early Bronze Age date (4th-3rd millennium BCE).
The initial laryngeal *h₂ produces the a-coloring visible in Latin aes and Sanskrit áyas-. Modern descendants include English ore, era, and the chemical symbol for copper, Cu (from Latin cuprum < Cyprium aes, "Cyprian metal").
Notes
Source of Latin "aes" (bronze), English "ore". Core metallurgical term.