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A. Richard Diebold Center for Indo-European Language and Culture

Indo-European Phonology

Proto-Indo-European Phonemes

Proto-Indo-European (PIE) phonemes included consonants, vowels, resonants, and laryngeals (see Lehmann's Proto-Indo-European Phonology and other manuals on Indo-European phonology). Click on phonemes in the tables below to access roots that exemplify their use, and then on roots to see attested words that support the reconstruction of the roots.


PIE consonant types included obstruents (stop consonants) and one fricative, /s/. Each sound is considered a phoneme here because, in roots, it appears in initial and/or final positions. In the table below, obstruents are transcribed using both traditional rendering (on the left side of '=') and "glottalic" rendering (on the right side).

Articulation   Bilabial   Dental   Palato-Velar*   Labio-Velar
Voiceless (aspiration optional)       P = P(h)   T = T(h)   K = K(h)   Kw = Kw(h)
Voiced ~ Voiceless glottalized       B = P'   D = T'   G = K'   Gw = K'w
Voiced (aspirated)       Bh = B(h)   Dh = D(h)   Gh = G(h)   Gwh = Gw(h)
FRICATIVE           S        
* In the table above, palatal and velar obstruents have been collapsed into a single column; distinctions between these types may be indicated elsewhere.

Two obstruent sets here are the traditionally reconstructed /p t k kw/, /b d g gw/, and /bh dh gh gwh/ vs. the "glottalic" /p(h) t(h) k(h) kw(h)/, /p' t' k' k'w/, and /b(h) d(h) g(h) gw(h)/. Equated pairs reflect two hypothetical views of Proto-Indo-European phonology: each system is based on the same attested forms, but has different implications for the way in which sounds may have changed in prehistory. Most handbooks reflect the traditional view. For more on the Glottalic Theory, see the section on phonology in Thomas V. Gamkrelidze & Vjaceslav V. Ivanov, Indo-European and the Indo-Europeans (1984 Russian original translated by Johanna Nichols; Berlin: de Gruyter, 1995, 2 vol's); a topical summary by Allan Bomhard appears in the Glottalic Theory section of our Reconstructing PIE Phonology page.

Consonants (C) and vowels (V) formed PIE roots of the shape CVC-. So, for example, the PIE root for 'foot' began with the consonant /p/ or glottalic /ph/, and ended with /d/ or glottalic /t'/. (Traditional *p corresponds to modern English /f/ and *d to modern English /t/; or, alternatively, glottalic *p(h) corresponds to modern English /f/ and glottalic *t' to modern English /t/.)


Vowels, as the nucleus of a root, might undergo vowel alternation (or ablaut). PIE was hypothesized to have one vowel, /e/, often alternating with [o] or lack of a vowel (a "zero vowel"). Such vowel alternation might vary the grammar, as it still does in English sing, sang, sung (with [in] of sing reflecting older [en]; [an] of sang, older [on]; and [un] of sung, older [n]).

    Front   Central   Back
Vowel       E   A   O


Both obstruents and the fricative /S/ always behaved as consonants in the CVC- root; but resonants could behave as either consonants or vowels, depending on their environment in a syllable. Resonants could function as a syllable nucleus in the absence of a vowel. When vowel alternation varied the grammar of a word, as in English 'sing, sang, sung', the lack of a root vowel put the resonant in a vocalic position. (N.B. English sung reflects PIE *sn.-gwh as vocalic resonant *n. regularly becomes /un/ in Germanic; vocalic resonants are usually transcribed with a ring below to distinguish them from consonantal resonants, but here, '.' follows a vocalic resonant.)

    Nasals   Liquids   Glides
Vocalic or Consonantal       M    N   R    L   W    Y

The resonsont (glide) *w in *wed- = *wet' 'wet, water' behaved as a consonant, but it too could have a vocalic counterpart. Not only did processes of vowel alternation ('wet, water') create new words but, as enlargements or suffixes created new word forms, a resonant might become a syllable nucleus. The root *wed-(r) = *wet'-(r) alternated with *ud-(r) = *ut'-(r) when the root vowel /e/ was reduced to zero; the resonant *w, as syllable nucleus, thus takes its vocalic form *u -- reflected in Greek (h)ud-or 'water', from which English borrowed hydrophobia 'water-fear'.


A theoretical class of sounds, laryngeals (H1, H2, H3), "colored" vowels on either side of them. The laryngeal H2, for example, colored an adjacent vowel /e/ with the value /a/. Similar to resonants, laryngeals also had consonantal or vocalic function depending on their position in a syllable.