IEI — Indo-European Isoglosses

IEI (Indo-European Isoglosses) is a database of phonological correspondences across attested Indo-European languages. Its aim is to represent, in an accessible format, the body of knowledge on regular Indo-European sound correspondences.

For each reconstructed Proto-Indo-European phoneme, the database records its reflexes in the daughter languages. On this basis, users can perform queries and visualise the resulting groupings of languages on a geographical map.

This platform is in active development and constitutes an early public release. While its core architecture and main functionalities are operational, the underlying dataset remains under systematic construction and validation. All outputs should therefore be considered provisional: apparent absences or distributions may reflect gaps in data coverage rather than established linguistic evidence. Details of both content and interface are subject to change.

Progress so far

The PIE model selection section is a global settings panel for choosing the phonological model of Proto-Indo-European adopted across the platform. Users can switch among several reconstructed systems — Szemerényi (1996), Hopper (1973), Gamkrelidze–Ivanov (1995) and Meier-Brügger (2003) — spanning the standard four-series notation, the glottalic theory and the modern laryngealist system. Switching model reloads the reconstruction (symbols, series, mergers and allophony) while leaving the underlying comparative correspondences unchanged.

The Attested phonologies section displays the phonemic inventories of a subset of Indo-European languages. Phonemes are arranged in standard phonological grids, with each item linked to its Proto-Indo-European sources. Selecting a phoneme reveals its features and its complete set of PIE ancestors.

The Correspondences section visualises the full set of PIE → outcome correspondences for a given language as an interactive three-level graph.

The Isogloss Explorer allows users to construct a query visually and to display the resulting geographical distribution across the Indo-European family on a map.

History

June 2026: multiple PIE phonological models implemented (Szemerényi, Hopper, Gamkrelidze–Ivanov, Meier-Brügger); underlying data store migrated from static JSON files to a relational MySQL database.
May 2026: first public release (early access); the platform is under active development and data coverage is being continuously expanded. Feedback is welcome (artemij.keidan@uniroma1.it).
2015–2026: initial development phase and first data entry.

Section status

Beta

PIE model

Four selectable models; the reconstruction is re-read live without altering the data.

Beta

Attested phonologies

Full phonological grids with PIE ancestry.

Beta

Correspondences

Interactive vector graph per language.

Beta

Isogloss Explorer

Visual query builder with geographical map.

PIE Consonants

PIE Vowels

Select a PIE phoneme to see its outcomes.

Consonants

Vowels

Select a phoneme.

Select a phoneme to show its Proto-Indo-European ancestors.

Correspondence Vectors

Red = languages matching the isogloss. Grey = languages not matching.

Query builder

SQL command

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Actions

Results

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Blog

Notes and essays tagged #IEI from my blog Śabdānuśāsana.

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Credits

Project credits and attributions
Conception and design	Artemij Keidan (opens in new tab) Italian Institute of Oriental Studies, Sapienza University of Rome artemij.keidan@uniroma1.it
Data curation	Artemij Keidan Alessandro del Tomba Andrea Di Manno All data are manually collected, curated, and annotated.
Technical development	Original implementation by Daniel Beilinson (opens in new tab). Subsequent development and extensions were carried out with the assistance of AI-based programming tools (Claude, Anthropic).
External libraries	D3.js (opens in new tab) (version 7) Open-source JavaScript library for data-driven and interactive visualisation. TopoJSON Client (opens in new tab) (version 3) JavaScript module for manipulating topological geospatial data.
Funding	Sapienza University of Rome The initial development phase was supported by a Sapienza University Research Office Grant (project title: Indo-European isoglosses: data collection and models of representation).
Copyright and licensing	© 2015–2026 Artemij Keidan All rights reserved. The database and its contents may not be reproduced, distributed, or reused without explicit permission.