Proto-Indo-European

Proto-Indo-European (PIE) is the hypothetical common ancestor of the Indo-European language family, reconstructed through the comparative method. Though no written records survive, systematic correspondences between daughter languages—from Hittite and Sanskrit to Latin, Greek, and English—allow linguists to infer the phonology, morphology, and lexicon of a language spoken roughly 4500–2500 BCE.

The reconstruction rests on regular sound correspondences first identified in the nineteenth century and refined continuously since. Where Latin has p, Greek has p, and Sanskrit has p, but Germanic shows f (Grimm’s Law), we reconstruct PIE p. Thousands of such correspondences, governed by dozens of named sound laws, underpin the reconstructed forms marked with an asterisk throughout this site.

This reference catalogues PIE roots, their reflexes across the attested daughter branches, the sound laws that governed their development, and the notation conventions used in the field. All content is open-access.