About
Mission
proto-indo-european.org documents the reconstructed lexicon of Proto-Indo-European, the unattested common ancestor of the Indo-European language family. The site presents reconstructed roots, their reflexes in attested daughter languages, and the sound laws that govern their development—organized for direct consultation by students, researchers, and working linguists.
The aim is not to replace the primary literature but to make it navigable. Each entry synthesizes findings from the major etymological dictionaries, notes points of scholarly disagreement, and cites its sources. Where the evidence is insufficient or contested, the site says so rather than presenting conjecture as consensus.
Methodology
All reconstructions follow the comparative method as formalized by the Neogrammarians and refined through subsequent scholarship. The procedure is well established: systematic sound correspondences among attested cognates in the daughter languages permit the inference of ancestral forms. Where Latin preserves pater, Greek patēr, and Sanskrit pitá, the correspondences are regular and the reconstruction ph₂tēr follows from them.
The site adopts the standard three-laryngeal hypothesis (h₁, h₂, h₃), which has represented the working consensus in the field since the mid-twentieth century. Ablaut grades are recorded using established notation. The full set of conventions—the asterisk, laryngeal symbols, ablaut notation, and IPA transcription—is described on the Notation page.
Each root entry carries a confidence assessment reflecting the state of current scholarship:
Sources
The reconstructions and descendant forms presented on this site draw on the following reference works, among others:
Beekes, Robert S. P. Etymological Dictionary of Greek. Leiden Indo-European Etymological Dictionary Series, vol. 10. Leiden: Brill, 2010.
Derksen, Rick. Etymological Dictionary of the Slavic Inherited Lexicon. Leiden Indo-European Etymological Dictionary Series, vol. 4. Leiden: Brill, 2008.
de Vaan, Michiel. Etymological Dictionary of Latin and the other Italic Languages. Leiden Indo-European Etymological Dictionary Series, vol. 7. Leiden: Brill, 2008.
Kroonen, Guus. Etymological Dictionary of Proto-Germanic. Leiden Indo-European Etymological Dictionary Series, vol. 11. Leiden: Brill, 2013.
Mallory, J. P., and Douglas Q. Adams. The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World. Oxford: Oxford University Press, 2006.
Pokorny, Julius. Indogermanisches etymologisches Wörterbuch. Bern: Francke, 1959. The classical PIE dictionary. Superseded in many specifics but remains an indispensable point of departure.
Rix, Helmut, et al. Lexikon der indogermanischen Verben: Die Wurzeln und ihre Primärstammbildungen. 2nd ed. Wiesbaden: Reichert, 2001. (LIV².) The standard reference for PIE verbal roots.
Watkins, Calvert. “Indo-European Roots.” Appendix to The American Heritage Dictionary of the English Language. 5th ed. Boston: Houghton Mifflin Harcourt, 2011.
Contributing
Registered contributors may submit annotations, corrections, and alternative analyses to any root entry. All submissions are reviewed before publication. Corrections that cite published sources are given priority.
To request contributor access, use the contact information below. Include your institutional affiliation or relevant background.
Access and Sponsorship
This site is free and open-access. There are no paywalls, display advertisements, or affiliate links. The project is sponsored by this project, which provides data infrastructure and hosting. Sponsorship does not influence editorial content.
Contact
For corrections, contributor requests, or scholarly inquiries, write to us through this project.