Proto-Indo-European phonology

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The phonology of the Proto-Indo-European language (PIE) has been reconstructed by linguists, based on the similarities and differences among current and extinct Indo-European languages. Because PIE was not written, linguists must rely on the evidence of its earliest attested descendants, such as Hittite, Sanskrit, Ancient Greek, and Latin, to reconstruct its phonology.

The reconstruction of abstract units of PIE phonological systems (i.e. segments, or phonemes in traditional phonology) is mostly uncontroversial, although areas of dispute remain. Their phonetic interpretation is harder to establish; this pertains especially to the vowels, the so-called laryngeals, the palatal and plain velars and the voiced and voiced aspirated stops.

Phonemic inventory[]

Proto-Indo-European is reconstructed to have used the following phonemes. See the article on Indo-European sound laws for a summary of how these phonemes reflected in the various Indo-European languages.

Consonants[]

The table gives the most common notation in modern publications; variant transcriptions are given below. Raised ʰ stands for aspiration, and raised ʷ for labialization. The *y corresponds to the palatal semivowel whose IPA transcription is [j] (and not to IPA [y]).

Stop series[]

Former reconstructions involved series of four stops: voiceless unaspirated and aspirated, and voiced unaspirated and aspirated: *t, *tʰ, *d, *dʰ. The voiceless aspirated stops, however, came to be reinterpreted as sequences of stop and laryngeal and so the standard reconstruction now includes series of only three, with the traditional phonetic descriptions of voiceless, voiced and voiced aspirated.

However, such a tripartite system is not found in any descendant language (Sanskrit had a fourfold distinction, including a voiceless aspirated series), and it is typologically rare across attested languages. The absence or rarity of *b (see below) is also unusual. Additionally, Proto-Indo-European roots have a constraint that forbids roots from mixing voiceless and voiced aspirate stops or from containing two voiced stops. All that has led some scholars to change the reconstruction by replacing the voiced stops by glottalized and the voiced aspirated stops by plain voiced. Direct evidence for glottalization is limited, but there is some indirect evidence, including Winter's law in Balto-Slavic as well as the parallel development of voiceless consonants and voiced aspirated consonants in Germanic: both became fricatives and glottalized (plain voiced in the earlier theory) consonants remained stops.

Labials and coronals[]

PIE *p, *b, *bʰ are grouped with the cover symbol P. The phonemic status of *b is disputed: it seems not to appear as an initial consonant (except in a few dubious roots such as *bel-, noted below), while reconstructed roots with internal *b are usually restricted to Western branches, casting doubt on their validity for PIE.^[1]

Some have attempted to explain away the few roots with *b as a result of later phonological developments.^[2] Suggested such developments include

• *ml- > *bl-, connecting the dubious root *bel- 'power, strength' (> Sanskrit bálam, Ancient Greek beltíōn) with mel- in Latin melior, and *h₂ebl-/*h₂ebōl 'apple' with a hypothetical earlier form *h₂eml-, which is in unmetathesized form attested in another reconstructible PIE word for apple, *méh₂lom (> Hittite maḫla-, Latin mālum, Ancient Greek mēlon).
• In PIE *ph₃ the *p regularly gives *b; for example, the reduplicated present stem of *peh₃- 'to drink' > *pi-ph₃- > Sanskrit píbati.

At best, PIE *b remains a highly marginal phoneme.

The standard reconstruction identifies three coronal, or dental, stops: *t, *d, *dʰ. They are symbolically grouped with the cover symbol T.

Dorsals[]

According to the traditional reconstruction, such as the one laid out in Brugmann's Grundriß der vergleichenden Grammatik der indogermanischen Sprachen more than a century ago, three series of velars are reconstructed for PIE:

• "Palatovelars" (or simply "palatals"), *ḱ, *ǵ, *ǵʰ (also transcribed *k', *g', *g'ʰ or *k̑, *g̑, *g̑ʰ or *k̂, *ĝ, *ĝʰ).
• "Plain velars" (or "pure velars"), *k, *g, *gʰ.
• Labiovelars, *kʷ, *gʷ, *gʷʰ (also transcribed *k^u̯, *g^u̯, *g^u̯h). The raised ʷ or ^u̯ stands for labialization (lip rounding) accompanying the velar articulation.

The actual pronunciation of these sounds in PIE is not certain. One current idea is that the "palatovelars" were in fact simple velars, i.e. *[k], *[ɡ], *[ɡʱ], while the "plain velars" were pronounced farther back, perhaps as uvular consonants, i.e. *[q], *[ɢ], *[ɢʱ].^[3] If the labiovelars were just labialized forms of the "plain velars", they would then have been pronounced *[qʷ], *[ɢʷ], *[ɢʷʱ] but the pronunciation of the labiovelars as *[kʷ], *[ɡʷ], *[ɡʷʱ] would still be possible in uvular theory, if the satem languages first shifted the "palatovelars" and then later merged the "plain velars" and "labiovelars". See Centum and satem languages § Different realisations for more support of this theory.

Another theory is that there may have been only two series (plain velar and labiovelar) in PIE, with the palatalized velars arising originally as a conditioned sound change in satem languages. See Centum and satem languages § Only two velar series.

The satem languages merged the labiovelars *kʷ, *gʷ, *gʷʰ with the plain velar series *k, *g, *gʰ, while the palatovelars *ḱ, *ǵ, *ǵʰ became sibilant fricatives or affricates of various types, depending on the individual language. In some phonological conditions, depalatalization occurred, yielding what appears to be a centum reflex in a satem language. For example, in Balto-Slavic and Albanian, palatovelars were depalatalized before resonants unless the latter were followed by a front vowel. The reflexes of the labiovelars are generally indistinguishable from those of the plain velars in satem languages, but there are some words where the lost labialization has left a trace, such as by u-coloring the following vowel.

The centum group of languages, on the other hand, merged the palatovelars *ḱ, *ǵ, *ǵʰ with the plain velar series *k, *g, *gʰ, while the labiovelars *kʷ, *gʷ, *gʷʰ were kept distinct. Analogous to the depalatalization of the satem languages, the centum languages show delabialisation of labiovelars when adjacent to *w (or its allophone *u), according to a rule known as the boukólos rule.

Fricatives[]

The only certain PIE fricative phoneme *s was a strident sound, whose phonetic realization could range from [s] to palatalized [ɕ] or [ʃ]. It had a voiced allophone *z that emerged by assimilation in words such as *nisdós ('nest'), and which later became phonemicized in some daughter languages. Some PIE roots have variants with *s appearing initially: such *s is called s-mobile.

The "laryngeals" may have been fricatives, but there is no consensus as to their phonetic realization.

Laryngeals[]

The phonemes *h₁, *h₂, *h₃ (or *ə₁, *ə₂, *ə₃ and /ə/), marked with cover symbol H (also denoting "unknown laryngeal"), stand for three "laryngeal" phonemes. The term laryngeal as a phonetic description is largely obsolete, retained only because its usage has become standard in the field.

The phonetic values of the laryngeal phonemes are disputable; various suggestions for their exact phonetic value have been made, ranging from cautious claims that all that can be said with certainty is that *h₂ represented a fricative pronounced far back in the mouth, and that *h₃ exhibited lip-rounding up to more definite proposals; e.g. Meier-Brügger writes that realizations of *h₁ = [h], *h₂ = [χ] and *h₃ = [ɣ] or [ɣʷ] "are in all probability accurate".^[4] Another commonly cited speculation for *h₁ *h₂ *h₃ is [ʔ ʕ ʕʷ] (e.g. Beekes). Simon (2013)^[5] has argued that the Hieroglyphic Luwian sign *19 stood for /ʔa/ (distinct from /a/) and represented the reflex of *h₁. It is possible, however, that all three laryngeals ultimately fell together as a glottal stop in some languages. Evidence for this development in Balto-Slavic comes from the eventual development of post-vocalic laryngeals into a register distinction commonly described as "acute" (vs. "circumflex" register on long vocalics not originally closed by a laryngeal) and marked in some fashion on all long syllables, whether stressed or not; furthermore, in some circumstances original acute register is reflected by a "broken tone" (i.e. glottalized vowel) in modern Latvian.

The schwa indogermanicum symbol *ə is sometimes used for a laryngeal between consonants, in a "syllabic" position.

Sonorants[]

In a phonological sense, sonorants in Proto-Indo-European were those segments that could appear both in the syllable nucleus (i.e. they could be syllabic) and out of it (i.e. they could be non-syllabic). PIE sonorants are the liquids, nasals and glides: more specifically, *r, *l, *n, *y (or *i̯) are non-labial sonorants, grouped with the cover symbol R, while labial sonorants *m, *w (or *u̯), are marked with the cover symbol M.

All of them had allophones in a syllabic position, which is generally between consonants, word-initially before consonants and word-finally after a consonant. They are marked as *r̥, *l̥,*m̥, *n̥, *i, *u. Even though *i and *u were phonetically certainly vowels, phonologically they were syllabic sonorants.

Reflexes[]

Some of the changes undergone by the PIE consonants in daughter languages are the following:

• Proto-Celtic, Albanian, Proto-Balto-Slavic and Proto-Iranian merged the voiced aspirated series *bʰ, *dʰ, *ǵʰ, *gʰ, *gʷʰ with the plain voiced series *b, *d, *ǵ, *g, *gʷ. (In Proto-Balto-Slavic this postdated Winter's law. Proto-Celtic retains the distinction between *gʷʰ and *gʷ - the former became *gw while the latter became *b.)
• Proto-Germanic underwent Grimm's law and Verner's law, changing voiceless stops into voiceless or voiced fricatives, devoicing unaspirated voiced stops, and fricativizing and deaspirating voiced aspirates.
• Grassmann's law (Tʰ-Tʰ > T-Tʰ, e.g. dʰi-dʰeh₁- > di-dʰeh₁-) and Bartholomae's law (TʰT > TTʰ, e.g. budʰ-to- > bud-dʰo-) describe the behaviour of aspirates in particular contexts in some early daughter languages.

Sanskrit, Greek, and Germanic, along with Latin to some extent, are the most important for reconstructing PIE consonants, as all of these languages keep the three series of stops (voiceless, voiced and voiced-aspirated) separate. In Germanic, Verner's law and changes to labiovelars (especially outside of Gothic) obscure some of the original distinctions; but on the other hand, Germanic is not subject to the dissimilations of Grassmann's law, which affects both Greek and Sanskrit. Latin also keeps the three series separate, but mostly obscures the distinctions among voiced-aspirated consonants in initial position (all except *gʰ become /f/) and collapses many distinctions in medial position. Greek is of particular importance for reconstructing labiovelars, as other languages tend to delabialize them in many positions.

Anatolian and Greek are the most important languages for reconstructing the laryngeals. Anatolian directly preserves many laryngeals, while Greek preserves traces of laryngeals in positions (e.g. at the beginning of a word) where they disappear in many other languages, and reflects each laryngeal different from the others (the so-called triple reflex) in most contexts. Balto-Slavic languages are sometimes valuable in reconstructing laryngeals since they are relatively directly represented in the distinction between "acute" and "circumflex" vowels. Old Avestan faithfully preserves numerous relics (e.g. laryngeal hiatus, laryngeal aspiration, laryngeal lengthening) triggered by ablaut alternations in laryngeal-stem nouns, but the paucity of the Old Avestan corpus prevents it from being more useful. Vedic Sanskrit preserves the same relics rather less faithfully, but in greater quantity, making it sometimes useful.

Vowels[]

It is disputed how many vowels Proto-Indo-European has or even what counts as a "vowel" in the language. It is generally agreed that at least four vowel segments existed, which are typically denoted as *e, *o, *ē and *ō. All of them are morphologically conditioned to varying extents. The two long vowels are less common than the short vowels, and their morphological conditioning is especially strong, suggesting that in an earlier stage there may not have been a length opposition, and a system with as few as two vowels (or even only one vowel, according to some researchers) may have existed.

In addition, the surface vowels *i and *u were extremely common, and syllabic sonorants *r̥, *l̥, *m̥, *n̥ existed. All of them alternated in a syllabic position with sonorant consonants *y, *w, *r, *l, *m, *n. For example, the root of the PIE word *yugóm ('yoke') with a *u also appears in the verb *yewg- ('to yoke, harness, join') with *w. Similarly, the PIE word *dóru ('tree, wood') is reconstructed with genitive singular *dréws and dative plural *drúmos. Some authors (e.g. Ringe (2006) harvcoltxt error: no target: CITEREFRinge2006 (help)) have argued that there is substantial evidence for reconstructing a non-alternating phoneme *i in addition to an alternating phoneme *y as well as weaker evidence for a non-alternating phoneme *u.

Furthermore, all the daughter languages have a segment *a, and those with long vowels generally have long /aː/, /iː/, /uː/. Until the mid-20th century, PIE was reconstructed with all of those vowels. Modern versions incorporating the laryngeal theory, however, tend to view the vowels as later developments of sounds that should be reconstructed in PIE as laryngeals *h₁, *h₂, h₃. For example, what used to be reconstructed as PIE *ā is now reconstructed as *eh₂; *ī, *ū are now reconstructed as *iH *uH, *H representing any laryngeal; and *a has various origins, among which are a "syllabic" [H̥] (any laryngeal not adjacent to a vowel) or an *e next to the "a-coloring" laryngeal *h₂e. (Though they may have phonetically contained the vowel [a] in spoken PIE, it would be an allophone of *e, not an independent phoneme.) Some researchers, however, have argued that an independent phoneme *a must be reconstructed, and it cannot be traced back to any laryngeal.

Any sonorant consonant can comprise the second part of a complex syllable nucleus; all can form diphthongs with any of the vowels *e, *o, *ē, *ō (such as *ey, *oy, *ēy, *ōy, *ew, *ow, *em, *en, etc.).

It is generally accepted that PIE did not allow vowels word-initially; the vowel-initial words in earlier reconstructions are now usually reconstructed as beginning with one of the three laryngeals; they disappeared in all daughter languages except Hittite before a vowel (after coloring it, if possible).

Lengthened vowels[]

In particular morphological (such as a result of Proto-Indo-European ablaut) and phonological conditions (like in the last syllable of nominative singular of a noun ending on sonorant, in root syllables in the sigmatic aorist, etc.; compare Szemerényi's law, Stang's law) vowels *e and *o would lengthen, yielding respective lengthened-grade variants. The basic lexical forms of words contained therefore only short vowels; forms with long vowels, *ē and *ō, appeared from well-established morphophonological rules.

Lengthening of vowels may have been a phonologically-conditioned change in Early Proto-Indo-European, but at the period just before the end of Proto-Indo-European, which is usually reconstructed, it is no longer possible to predict the appearance of all long vowels phonologically, as the phonologically-justified resulting long vowels have begun to spread analogically to other forms without being phonologically justified. The prosodically-long *e in *ph₂tḗr 'father' results by the application of Szemerényi's law, a synchronic phonological rule that operated within PIE, but prosodically-long *o in *pṓds 'foot' was analogically levelled.

/a/[]

It is possible that Proto-Indo-European had a few morphologically-isolated words with the vowel *a: *dap- 'sacrifice' (Latin daps, Ancient Greek dapánē, Old Irish dúas) or appearing as a first part of a diphthong *ay: *laywos 'left' (Latin laevus, Ancient Greek laiós, OCS lěvъ). The phonemic status of *a has been fiercely disputed; Beekes^[6] concludes: "There are thus no grounds for PIE phoneme *a"; his former student, Alexander Lubotsky, reaches the same conclusion.^[7]

After the discovery of Hittite and the development of the laryngeal theory, almost every instance of previous *a could be reduced to the vowel *e preceded or followed by the laryngeal *h₂ (rendering the previously reconstructed short and long *a, respectively). Against the possibility of PIE phoneme *a, still today held by some Indo-Europeanists, the following can be said: vowel *a does not participate in ablaut alternations (it does not alternate with other vowels, as the "real" PIE vowels *e, *o, *ē, *ō do), it makes no appearance in suffixes and endings, it appears in a very confined set of positions (usually after initial *k, which could be the result of that phoneme being a-coloring, particularly likely if it was uvular /q/), and the reflexes of words upon which *a is reconstructed are usually confined only to a few Indo-European languages. For example, *bʰardʰéh₂ 'beard,' is confined to the western and northern daughter families. That makes it possible to ascribe it to some late PIE dialectalism or of expressive character (like the interjection *way 'alas') and so is not suitable for comparative analysis, or they are argued to have been borrowed from some other language which had phonemic *a (like Proto-Semitic *θawru > PIE *táwros ('aurochs')).

However, others, like Manfred Mayrhofer,^[8] argue that *a and *ā phonemes existed independently of *h₂. This phoneme appears to be present in reconstructions such as *albʰós ("white"), or *átta ("father"), where the absence of a laryngeal is suggested by the respective Hittite descendants; WIKI