User:Meuser2/Storage/PIE language topics

=The Language= Proto-Indo-European is the linguistic reconstruction of a common ancestor of the Indo-European languages spoken by the Proto-Indo-Europeans. PIE was the first proposed proto-language to be widely accepted by linguists. Far more work has gone into reconstructing it than any other proto-language and it is by far the best understood of all proto-languages of its age. During the 19th century, the vast majority of linguistic work was devoted to reconstruction of Proto-Indo-European or its daughter proto-languages such as Proto-Germanic, and most of the current techniques of linguistic reconstruction in historical linguistics (e.g. the comparative method and the method of internal reconstruction) were developed as a result.

The existence of PIE was first postulated in the 18th century by Sir William Jones, who observed the similarities between Sanskrit, Ancient Greek, and Latin. By the early 20th century, well-defined descriptions of PIE had been developed that are still accepted today (with some refinements). The largest developments of the 20th century were the discovery of the Anatolian and Tocharian languages and the acceptance of the laryngeal theory. The Anatolian languages have also spurred a major re-evaluation of theories concerning the development of various shared Indo-European language features and the extent to which these features were present in PIE itself.

PIE is thought to have had a complex system of morphology that included inflections (suffixing of roots, as in who, whom, whose), and ablaut (vowel alterations, as in sing, sang, sung). Nouns used a complicated system of declension and verbs used a similarly complicated system of conjugation.

Relationships to other language families, including the Uralic languages, have been proposed but remain controversial.

There is no written evidence of Proto-Indo-European, so all knowledge of the language is derived by linguists from later languages using the comparative method and internal reconstruction.

Root
PIE was an inflected language, in which the grammatical relationships between words were signaled through inflectional morphemes (usually endings). The roots of PIE are basic morphemes carrying a lexical meaning. By addition of suffixes, they form stems, and by addition of desinences (usually endings), these form grammatically inflected words (nouns or verbs). PIE roots are understood to be predominantly monosyllabic with a basic shape CvC(C). This basic root shape is often altered by ablaut. Roots which appear to be vowel initial are believed by many scholars to have originally begun with a set of consonants, later lost in all but the Anatolian branch, called laryngeals (specified with a subscript number ). Thus a verb form such as the one reflected in Latin agunt, Greek ἄγουσι (ágousi), Sanskrit would be reconstructed as, with the element  constituting the root per se.

Ablaut
An important component of PIE morphophonology is the variation in vowels commonly termed ablaut, which occurred both within inflectional morphology (different grammatical forms of a noun or verb) and derivational morphology (between, for example, a verb and an associated verbal noun). Ablaut in PIE was closely associated with the position of the accent; for example, the alternation found in Latin est, sunt reflects PIE. However, it is not possible to derive either one directly from the other. The primary ablaut variation was between normal grade or full grade ( and ), lengthened grade ( and ), and zero grade (lack of a vowel, which affected nearby sonorant consonants such as l,m,n and r). The normal grade is often characterized as e-grade or o-grade depending on the particular vowel involved. Ablaut occurred both in the root and the ending. Often the zero-grade appears where the word's accent has shifted from the root to one of the affixes.

Originally, all categories were distinguished both by ablaut and different endings, but the loss of endings in some later Indo-European languages has led them to use ablaut alone to distinguish grammatical categories, as in the Modern English words sing, sang, sung, originally reflecting a pre-Proto-Germanic sequence *sengw-, *songw-, *sngw-.

Noun
Proto-Indo-European nouns were declined for eight or nine cases (nominative, accusative, genitive, dative, instrumental, ablative, locative, vocative, and possibly a directive or allative). There were three genders: masculine, feminine, and neuter.

There are two major types of declension, thematic and athematic. Thematic nominal stems are formed with a suffix (in vocative ) and the stem does not undergo ablaut. The athematic stems are more archaic, and they are classified further by their ablaut behaviour (acrostatic, proterokinetic, hysterokinetic and amphikinetic, after the positioning of the early PIE accent in the paradigm).

Pronoun
PIE pronouns are difficult to reconstruct owing to their variety in later languages. This is especially the case for demonstrative pronouns. PIE had personal pronouns in the first and second person, but not the third person, where demonstratives were used instead. The personal pronouns had their own unique forms and endings, and some had two distinct stems; this is most obvious in the first person singular, where the two stems are still preserved in English I and me. According to Beekes, there were also two varieties for the accusative, genitive and dative cases, a stressed and an enclitic form.

As for demonstratives, Beekes tentatively reconstructs a system with only two pronouns: "this, that" and  "the (just named)" (anaphoric). He also postulates three adverbial particles "here",  "there" and  "away, again", from which demonstratives were constructed in various later languages.

Verb
The Indo-European verb system is complex and, like the noun, exhibits a system of ablaut. The most basic categorization for the Indo-European verb was grammatical aspect. Verbs were classed as stative (verbs that depict a state of being), imperfective (verbs depicting ongoing, habitual or repeated action) or perfective (verbs depicting a completed action or actions viewed as an entire process). Verbs have at least four moods (indicative, imperative, subjunctive and optative, as well as possibly the injunctive, reconstructible from Vedic Sanskrit), two voices (active and mediopassive), as well as three persons (first, second and third) and three numbers (singular, dual and plural). Verbs were also marked by a highly developed system of participles, one for each combination of tense and voice, and an assorted array of verbal nouns and adjectival formations.

The following table shows two possible reconstructions of the PIE verb endings. Sihler's reconstruction largely represents the current consensus among Indo-Europeanists, while Beekes' is a radical rethinking of thematic verbs; although not widely accepted, it is included to show an example of more far-reaching recent research.

Numbers
The Proto-Indo-European numerals are generally reconstructed as follows: Lehmann believes that the numbers greater than ten were constructed separately in the dialect groups and that originally meant "a large number" rather than specifically "one hundred".

Particle
Many particles could be used both as adverbs and postpositions, like "under, below". The postpositions became prepositions in most daughter languages. Other reconstructible particles include negators, conjunctions ( "and", "or" and others) and an interjection (, an expression of woe or agony).

Generally accepted subfamilies (clades)

 * Proto-Albanian language
 * Proto-Anatolian language
 * Proto-Armenian language
 * Proto-Balto-Slavic language
 * Proto-Celtic language
 * Proto-Germanic language
 * Proto-Greek language
 * Proto-Indo-Iranian language
 * Proto-Italic language
 * Proto-Tocharian language

Marginally attested languages
These include languages that do not appear to be members of any of the above families, but which are so poorly attested that proper classification of them is not possible. Of these languages, Phrygian is easily the best attested.


 * Phrygian language
 * Dacian language
 * Thracian language
 * Illyrian language
 * Venetic language
 * Messapic language
 * Ancient Macedonian language
 * Lusitanian language

All of the above languages except for Lusitanian (which occurs in the area of modern Portugal) occur in or near the Balkan peninsula, and have been collectively termed the "Paleo-Balkan languages". This is a purely geographic grouping and makes no claims about the relatedness of the languages to each other as compared with other Indo-European languages.

Hypothetical clades

 * Italo-Celtic
 * Graeco-Aryan
 * Graeco-Armenian
 * Daco-Thracian
 * Thraco-Illyrian

Phonemic inventory
Proto-Indo-European is traditionally 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 stands for aspiration.

Labials
PIE are conveniently grouped with the cover symbol P. The phonemic status of is disputed: it only appears in handful of reconstructible roots that themselves are often disputed. All of the reconstructed roots with */b/ inside are usually confined to a few Indo-European branches, likely representing late PIE dialectalism.

Some have attempted to explain away the few roots with */b/ as a result of recent phonological developments. Suggested such developments include
 * *ml- > *bl-, connecting the 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 in PIE; for example, the reduplicated present stem of *peh₃- 'to drink' > *pi-ph₃- > Sanskrit píbati.

At best, PIE remains a highly marginal phoneme.

Coronals/dentals
The standard reconstruction identified three coronal/dental stops:. They are symbolically grouped with the cover symbol T.

In so-called "thorn clusters" of the form TK in all branches except Anatolian and Tocharian a metathesis occurred, resulting in dorsal-coronal clusters of non-obvious phonetic makeup. Metathetized and unmetathetized forms survive in different ablaut grades of the root * "burn" (whence also English day) in Sanskrit, ' "is being burnt" < * and '  "burns" < *. See the section on PIE phonological rules, below, for more discussion and examples.

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"), (also transcribed   or  or.
 * "Plain velars" (or "pure velars"),.
 * Labiovelars, (also transcribed ). Raised  stands for labialisation (lip-rounding) accompanying the articulation of velar sounds.

The terms "palatovelar" and "plain velar" are in quotes because they are traditional terms but are unlikely to represent the actual pronunciation of these sounds in PIE. One current idea is that the "palatovelars" were in fact simple velars, i.e., while the "plain velars" were pronounced farther back, perhaps actually uvular consonants, i.e. . Meanwhile, the labiovelars were exactly like the "plain velars" but labialized, i.e.  in the current understanding. These conclusions are suggested by the following evidence:


 * The "palatovelar" series was the most common; meanwhile the "plain velar" was by far the least common, and never occurred in any affixes. In known languages with multiple velar series, the normal velar series is usually the most common.


 * There is no evidence whatsoever of there ever having been any palatalization in the early history of the velars in any of the centum branches. If the "palatovelars" were in fact palatalized in PIE, there would have had to be a single, very early, uniform depalatalization in all (and only) the centum branches &mdash; depalatalization is cross-linguistically far less likely than palatalization, and hence unlikely to have occurred separately in each centum branch, and if such a situation did occur, it almost certainly would have left evidence of prior palatalization in some of the branches.  However, there is no evidence at all that the centum branches ever formed a clade (i.e. possess a common ancestor that is later than PIE as a whole, in which the putative depalatalization would have occurred).  Quite the contrary, some evidence indicates that Anatolian and Tocharian, two of the centum branches (note, however, that the Luwian branch of Anatolian seems to have satem reflexes, and Melchert reconstructs the palatal stops traditionally assumed for PIE for Proto-Anatolian, as well), were the first and second branches, respectively, to have split off from PIE, but this is uncertain and disputed.

Three velar series
The existence of all three dorsal columns (series) has been disputed since the beginning of Indo-European studies. Today, most PIE linguists believe that all three series were distinct by the time of Late Proto-Indo-European, although a minority believe that the distinction between plain velar and palatovelar consonants was a later development of certain satem languages; this belief was originally articulated by Antoine Meillet in 1894 and argued more recently by Frederik Kortlandt and others. This argument contends that PIE had only two series, a simple velar and a labiovelar. The satem languages palatalized the plain velar series in most positions, but the plain velars remained in some environments. These environments are typically reconstructed as before or after /u/, after /s/, and before /r/ or /a/; also apparently before /m/ and /n/ in some Baltic dialects. (This is conceptually similar to the change in Proto-Germanic whereby e.g. /t/ became /θ/ in most instances, but remained as /t/ after original /s/, /k/ or /p/.) The original allophonic distinction was disturbed when the labiovelars were merged with the plain velars. This produced a new phonemic distinction between palatal and plain velars, with an unpredictable alternation between palatal and plain in related forms of some roots (those from original plain velars) but not others (those from original labiovelars). Subsequent analogical processes generalized either the plain or palatal consonant in all forms of a particular root. Those roots where the plain consonant was generalized are those traditionally reconstructed as having "plain velars" in the parent language, in contrast to "palatovelars".

The basic arguments in favor of two velar series are:
 * The plain velar series is statistically rarer than the other two, is almost entirely absent from affixes, and appears most often in certain phonological environments (described above).
 * Alternations between plain velars and palatals are common in a number of roots across different satem languages, where the same root appears with a palatal in some languages but a plain velar in others (most commonly Baltic or Slavic; occasionally Armenian, but rarely or never the Indo-Iranian languages). This is consistent with the analogical generalization of one or another consonant in an originally alternating paradigm, but difficult to explain otherwise.
 * The above explanation suggests that in Late PIE times the satem languages were in close contact with each other. This is confirmed by independent evidence: The geographical closeness of current satem languages and certain other shared innovations (the Ruki sound law and early palatalization of velars before front vowels).
 * The traditional explanation of a three-way dorsal split requires that all centum languages share a common innovation that eliminated the palatovelar series. Unlike for the satem languages, however, there is no evidence of any areal connection among the centum languages, and in fact there is evidence against such a connection—the centum languages are geographically noncontiguous.  Furthermore, if such an areal innovation happened, we would expect to see some dialect differences in its implementation (cf. the above differences between Balto-Slavic and Indo-Iranian), and residual evidence of a distinct palatalized series (such evidence for a distinct labiovelar series does exist in the satem languages; see below).  In fact, however, neither type of evidence exists, suggesting that there was never a palatovelar series in the centum languages.

The basic arguments in favor of three velar series are:
 * Many instances of plain velars occur in roots that have no evidence of any of the putative environments that trigger plain velars, and no obvious mechanism for the plain velar to have come in contact with any such environment; as a result, the comparative method requires us to reconstruct three series.
 * Evidence from the Anatolian language Luwian attests a three-way velar distinction > z (probably );  > k;  > ku (probably ).  There is no evidence of any connection between Luwian and any satem language (labiovelars are still preserved, Ruki sound law is absent), and the Anatolian branch split off very early from PIE.  Hence, the three-way distinction must be reconstructed for the parent language. (This is a strong argument in favor of the traditional three-way system; in response, proponents of the two-way system have attacked the underlying evidence, claiming that it "hinges upon especially difficult or vague or otherwise dubious etymologies" (e.g. Sihler 1995).) Melchert originally claimed that the change  > z was unconditional, and subsequently revised the assertion to a conditional change occurring only before front vowels, /y/, or /w/; however, this does not fundamentally alter the situation, as plain-velar  apparently remains as such in the same context.  Melchert also asserts that, contrary to Sihler, the etymological distinction between  and  in the relevant positions is well-established.
 * According to Ringe (2006), there are root constraints that prevent the occurrence of a "palatovelar" and labiovelar, or two "plain velars", in the same root; but these do not apply to roots containing, e.g. a palatovelar and plain velar.

It should be noted that there is residual evidence of various sorts in the satem languages of a former distinction between velar and labiovelar consonants:


 * In Sanskrit and Balto-Slavic, in some environments, resonant consonants (denoted by /R/) become /iR/ after plain velars but /uR/ after labiovelars.
 * In Armenian, some linguists assert that /kʷ/ is distinguishable from /k/ before front vowels
 * Some linguists assert that in Albanian, /kʷ/ and /gʷ/ are distinguishable from /k/ and /g/ before front vowels

This evidence shows that the labiovelar series was distinct from the plain velar series in PIE, and cannot have been a secondary development in the centum languages; but it says nothing about the palatovelar vs. plain velar series.

In addition, modern proponents of the three-way distinction do not deny the final two points made in the arguments in favor of the two-way distinction, concerning the unity of the satem group and lack of such unity in the centum group. Rather, they claim that the centum change did indeed occur independently in multiple centum subgroups (at the very least, Tocharian, Anatolian and Western IE), but was a phonologically natural change given the current interpretation of the "palatovelar" series as plain-velar and the "plain velar" series as back-velar or uvular, and given the minimal functional load of the plain-velar/palatovelar distinction. Since there was never any palatalization in the IE dialects leading to the centum languages, there is no reason to expect any palatal residues; furthermore, it is phonologically entirely natural that a former plain-velar vs. back-velar/uvular distinction would leave no distinctive residues on adjacent segments.

It is quite possible to use the traditional three-way distinction while remaining agnostic on the issue of whether it represents the actual state of the parent language or is an artifact of later developments in the satem branch. It is also quite possible to take a compromise position asserting that the three-way distinction did indeed exist in late PIE but simultaneously did in fact develop from an earlier two-way distinction through the same mechanism and in the same environments traditionally claimed to have triggered the plain/palatal distinction in the satem languages.

Fricatives
The only certain PIE fricative phoneme was a strident sound, whose phonetic realization could possibly 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, with cover symbol  also denoting "unknown laryngeal" (or and ), stand for three  "laryngeal" phonemes. One should note that the term laryngeal as a phonetic description is out of date, 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  represented a fricative pronounced far back in the mouth, and that  exhibited lip-rounding up to more definite proposal; e.g. Meier-Brügger writes that realizations of  =,  =  and  =  or  "are in all probability accurate". Other commonly cited speculations for   are  (e.g. Beekes) and. It is sometimes claimed that may have been two consonants,  and, that fell together. A consensus seems to be emerging, however, that is unlikely to have been a glottal stop, as all three laryngeals pattern similarly to each other and to fricatives in other languages (and similarly to PIE /s/, the only other fricative); in contrast, Simon (2013) has argued that the Hieroglyphic Luwian sign *19 stood for /ʔa/ (distinct from /a/) and represents the reflex of. 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.

Glottalic theory
The phonetical values of the three stop series are traditionally reconstructed as voiceless (e.g. */t/), voiced (e.g. */d/) and voiced aspirated (e.g. */dʰ/). However, this system is not found in any descendant language (Sanskrit still has all three, but has added a fourth series of voiceless aspirated, e.g. /tʰ/), and is vanishingly rare in any recorded languages. The rarity of */b/ is also unusual. Additionally, PIE roots have a constraint which prohibits roots mixing voiceless and voiced aspirate stops, as well as roots containing two voiced stops. These facts have led some scholars to reassess this part of the reconstruction, 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, and in the fact that the voiceless consonants and the voiced aspirate consonants develop in parallel in Germanic, with both becoming fricatives while the glottalised (plain voiced in traditional theory) consonants remain stops.

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:, all grouped with the cover symbol R.

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:. One should note that, even though *i and *u were phonetically certainly vowels, phonologically they were syllabic sonorants.

Introduction
It is disputed how many vowels Proto-Indo-European (PIE) had, as well as what counts as a "vowel" in that language. It is generally agreed that at least four vowel segments existed, normally denoted as */e/, */o/, */ē/ and */ō/. All of these vowels 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 existed. All of these alternate 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. ) have argued that there is strong evidence for reconstructing a non-alternating phoneme *i in an addition to an alternating phoneme *y, as well as weaker evidence for a non-alternating phoneme *u.

In addition, all daughter Indo-European languages have a segment */a/, and those languages with long vowels generally have long. Up until the mid-20th century, PIE was reconstructed with all of these vowels. Modern versions incorporating the laryngeal theory, however, tend to view these vowels as later developments of sounds that should be reconstructed in PIE as laryngeals. For example, what used to be reconstructed as PIE is now reconstructed as ;  are now reconstructed as, where *H represents any laryngeal; and  has various origins, among which are a "syllabic"  (i.e. any laryngeal when not adjacent to a vowel, or an *e next to the "a-coloring" laryngeal . Some researchers, however, have argued that a phoneme *a must be reconstructed that cannot be traced back to any laryngeal.

Any of the sonorant consonants can comprise the second part of a complex syllable nucleus, i.e. they can form diphthongs with any of the vowels *e, *o, *ē, *ō; e.g. *ey, *oy,, */ew/, */ow/, */em/, */en/, etc.

Lengthened vowels
In certain morphological (e.g., as a result of Proto-Indo-European ablaut) and phonological conditions (e.g. in the last syllable of nominative singular of a noun ending on sonorant, in root syllable in sigmatic aorist etc.; cf. Szemerényi's law, Stang's law) vowels *e and *o would lengthen, yielding respective lengthened-grade variants. Basic, lexical forms of words in PIE contain therefore only short vowels; on the basis of well-established morphophonological rules forms with long vowels *ē and *ō appear.

Lengthening of vowels may have been a phonologically conditioned change in Early Proto-Indo-European, but at the period just before the dissolution of Proto-Indo-European speaking community, which is usually reconstructed, it is not possible to phonologically predict the appearance of all long vowels, because the phonologically justified resulting long vowels have begun to spread analogically to other forms in which they were not phonologically justified. Hence, the prosodically long */e/ in 'father' results by the application of Szemerényi's law, a synchronic phonological rule that operated within the PIE, but prosodically long */o/ in  'foot' is analogically leveled.

/a/
It is possible that Proto-Indo-European had a few morphologically isolated words that contained the vowel *a, e.g. *dap- 'sacrifice' (Latin daps, Ancient Greek dapánē, Old Irish dúas); or appearing as a first part of a diphthong *ay, e.g. *laywos 'left' (Latin laevus, Ancient Greek laiós, OCS lěvъ). The phonemic status of *a has been fiercely disputed; for example Beekes expressly concludes: There are thus no grounds for PIE phoneme *a, and the same conclusion is reached by his former student Alexander Lubotsky. After the discovery of Hittite and the advent of laryngeal theory, basically every instance of previous *a could be reduced to the vowel *e either preceded or followed by the laryngeal *h₂ (rendering the previously reconstructed short and long *a, respectively). Against the possibility of PIE phoneme *a, that is even today held by some Indo-Europeanists, the following can be said: vowel *a does not participate in ablaut alternations (i.e. 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 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 in fact uvular /q/) and the reflexes of words upon which *a is reconstructed are usually confined only to a few Indo-European languages which makes it possible to ascribe it to some late PIE dialectalism, or are of expressive character thus not being suitable for comparative analysis, or are argued to have been borrowed from some other language which had phonemic *a (e.g. Proto-Semitic *θawru > PIE *táwros "wild bull, aurochs").

However, others, like Mayrhofer, argue that PIE did in fact have and  phonemes independent of.

Accent
PIE had a free pitch accent, which could appear on any syllable and whose position often varied among different members of a paradigm (e.g. between singular and plural of a verbal paradigm, or between nominative/accusative and oblique cases of a nominal paradigm). The location of the pitch accent is closely associated with ablaut variations, especially between normal-grade vowels (/e/ and /o/) and zero-grade vowels (i.e. lack of a vowel).

Generally, thematic nouns and verbs (those with a "thematic vowel" between root and ending, usually /e/ or /o/) had a fixed accent, which (depending on the particular noun or verb) could be either on the root or the ending. These words also had no ablaut variations within their paradigms. (However, accent and ablaut were still associated; for example, thematic verbs with root accent tended to have e-grade ablaut in the root, while those ending accent tended to have zero-grade ablaut in the root.) On the other hand, athematic nouns and verbs usually had mobile accent, with varied between strong forms, with root accent and full grade in the root (e.g. the singular active of verbs, and the nominative and accusative of nouns), and weak forms, with ending accent and zero grade in the root (e.g. the plural active and all forms of the middle of verbs, and the oblique cases of nouns). Some nouns and verbs, on the other hand, had a different pattern, with ablaut variation between lengthened and full grade and mostly fixed accent on the root; these are termed Narten stems. Additional patterns exist for both nouns and verbs. For example, some nouns (so-called acrostatic nouns, one of the oldest classes of noun) has fixed accent on the root, with ablaut variation between o-grade and e-grade, while hysterodynamic nouns have zero-grade root with a mobile accent that varies between suffix and ending, with corresponding ablaut variations in the suffix.

The accent is best preserved in Vedic Sanskrit and (in the case of nouns) Ancient Greek. It is also reflected to some extent in the accentual patterns of the Balto-Slavic languages (e.g. Latvian, Lithuanian and Serbo-Croatian). It is indirectly attested in a number of phenomena in other PIE languages, especially the Verner's law variations in the Germanic languages. In other languages (e.g. the Italic languages and Celtic languages) it was lost without a trace. Other than in Modern Greek, the Balto-Slavic languages and (to some extent) Icelandic, few traces of the PIE accent remain in any modern languages.

Phonological rules
A number of phonological rules can be reconstructed for Proto-Indo-European. Some of them are disputed to be valid for "PIE proper", and are claimed to be later innovations in some of the daughter branches. Some of these laws are:


 * 1) Bartholomae's law:  >
 * Passive participle of 'to learn, become aware of': * > * > (Grassmann's law) Sanskrit buddhá.
 * Law has been preserved in Indo-Iranian branch where it operates as a synchronic rule. There are some traces of it in Ancient Greek and Germanic, and possibly in Latin.
 * 1) Dental assibilation: TT > TsT (a sequence of two dental stops had dental fricative */s/ inserted between them)
 * 'eats' > > Hittite ezzi.
 * This has been preserved in Hittite where cluster *tst is spelled as z (pronounced as [ts]). The cluster was often simplified to -ss- in the later descendants (Latin and Germanic among others).
 * 1) TK > KT > "Kþ" ("thorn clusters"): Dental stops that were placed behind PIE dorsals in the same syllable metathesized in all branches except in Tocharian and Anatolian (the earliest one that were to split from PIE matrix).  Subsequent outcomes were varied.
 * 'bear' > > Latin ursus, Ancient Greek árktos, Sanskrit ṛ́kṣas but Hittite ḫartaggas /ḫartkas/ without metathesis.
 * 'decaying, decline, ruin' > > Ancient Greek phthísis, Sanskrit kṣítis, perhaps Latin sitis
 * 1) Siebs' law: If s-mobile is added to the root that starts with voiced or aspirated stop, that stop is devoiced.
 * > Latin fragor, but >  > Sanskrit sphūrjati
 * 1) Stang's law: *Vwm > *Vːm; i.e. */w/ disappears and the preceding vowel lengthens in the last syllable behind word-final */m/. Some also add rules:  *Vmm > *Vːm and * > *Vːm; and also *Vyi > *Vːy.
 * *dyéwm 'sky' (accusative singular) > *dyḗm > Sanskrit dyā́m, acc. sg. of dyaús
 * * 'cattle' (acc. sg.) > * > Sanskrit gā́m, acc. sg. of gaús
 * accusative singular of * 'house' is, not.
 * 1) Szemerényi's law: -VRs > VːR,  >  i.e. in word-final sequences of vowel, sonorant and */s/ or */h₂/ the fricative or laryngeal was dropped and the preceding vowel lengthened. This affected nominative singulars of numerous masculine and feminine nouns, as well as the nominoaccusative of neuter collectives.
 * 'father' > > Ancient Greek patḗr, Sanskrit pitā́
 * 1) Laryngeal deletion rules: See below.

Thorn clusters
A problem in the reconstruction of PIE concerns some cognate sets in which Indo-Iranian sibilants in clusters with dorsals exceptionally correspond to coronal stops in certain other branches. 'Bear' and 'decaying' above are examples; some others are Sanskrit tákṣan 'artisan' vs. Greek téktōn 'carpenter', and Sanskrit kṣā́ḥ vs. Greek khthon both 'earth'. As was the case with the laryngeal theory, these cognate sets were first noted prior to the connection of Anatolian and Tocharian to PIE, and early reconstructions posited a new series of consonants to explain these correspondences. Brugmann 1897's systematic explanation augmented the PIE consonant system with a series of interdentals (nowhere directly attested) appearing only in clusters with dorsals, *kþ *khþh *gð *ghðh. The use of the letter thorn led to the name "thorn cluster" for these groups.

Anatolian and Tocharian evidence suggests that the original form of the thorn clusters was in fact *TK: Hittite has tēkan, tagnās, dagān and Tocharian A tkaṃ, tkan- for case-forms of 'earth', so that the development outside Anatolian and Tocharian involved a metathesis. The conventional notations *þ *ðʰ for the second elements of these metathesised clusters are still found, and some, including Fortson, continue to hold to the view that interdental fricatives were involved at some stage of PIE.

An alternative interpretation (e.g. Vennemann 1989, Schindler 1991 (informally and unpublished)) identifies these segments as alveolar affricates. In this view, thorn clusters developed as TK > TsK > KTs and then variously in daughter languages; this has the advantage that the first change can be identified with the dental assibilation rule above, which is then broadened in application to affrication of dental stops before any stops. Melchert has interpreted the Cuneiform Luvian īnzagan- 'inhumation', probably [ind͡zgan], from * 'in the earth', as preserving the intermediate stage of this process.

Laryngeal deletion rules
Once the laryngeal theory was developed, and the rules for sound change of laryngeals worked out, it was clear that there were a number of exceptions to the rules, in particular with regard to "syllabic" laryngeals (former "schwa indogermanicum") that occurred in non-initial syllables. It was long suggested that such syllabic laryngeals were simply deleted in certain of the daughters; this is based especially on the PIE word dhugh₂tér- "daughter", which appears in a number of branches (e.g. Germanic, Balto-Slavic) with no vowel in place of expected /a/ for "syllabic" /h₂/ (cf. English "daughter", Gothic daúhtar). With a better understanding of the role of ablaut, however, and a clearer understanding of which roots did and did not have laryngeals in them, it became clear that this suggestion cannot be correct. In particular, there are some cases where syllabic laryngeals in medial syllables delete in most or all daughter languages, and other cases where they do not delete even in Germanic and/or Balto-Slavic.

This has led to the more recent idea that PIE had a number of synchronic "laryngeal deletion" rules, where syllabic laryngeals in certain contexts were deleted even in the protolanguage. In the case of dhugh₂tér-, for example, it appears that PIE had an alternation between a "strong" stem dhugh₂tér- and a "weak" stem dhugtr-, where a deletion rule eliminated the laryngeal in the latter context but not the former one. Forms in daughter languages with or without the laryngeal are due to analogical generalization of one or the other protoforms.

This is a new area, and as a result there is no consensus on the number and nature of the deletion rules. A wide variety of rules have been proposed; Ringe (2006) identifies the following three as the most likely candidates (where C=any consonant, V=any vowel, H=any laryngeal, R=any resonant):


 * 1) A laryngeal in the sequence oRHC was dropped. Example: *tórmos "borehole" from *terh₁- "bore" (cf. Gk tórmos "socket", OE þearm "intestine").  This seems to have operated particularly in the thematic optative suffix -oy-h₁-, which was reduced to -oy- in most forms.
 * 2) A laryngeal in the sequence VCHy was dropped. Examples: *wérye- "say" (present tense) from *werh₁- (cf. Homeric Greek eírei "(he) says", not *eréei); h₂érye- "plow" (present tense) from h₂erh₃- "plow" (cf. Lith. ãria "(he) plows", not *ária).
 * 3) A laryngeal in the sequence CH-CC was dropped, where a syllable boundary follows the laryngeal (i.e. the following two consonants are capable of occurring at the start of a word, as in tr- but not rt-). An example is the weak stem dhugtr- given above, compared to the strong stem dhugh₂tér-.

It seems unlikely that this is a correct and complete description of the actual phonological rules underlying laryngeal deletion. These rules do not account for all the potential cases of laryngeal deletion (hence the many other rules that have been proposed); for example, the laryngeal in the desiderative suffixes -h₁s- and -h₁sy- appears to delete after an obstruent but not a resonant. In any case it is difficult to determine when a particular laryngeal loss is due to a protolanguage rule vs. an instance of later analogy. In addition, as synchronic phonological rules the set of above rules is more complex than what is expected from a cross-linguistic standpoint, suggesting that some of the rules may have already been "morphologized" (incorporated into the morphology of certain constructions, such as the o-grade noun-forming rule or the rule forming y-presents); the above-mentioned laryngeal deletion in the desiderative suffixes may be an example of such morphologization.

Phonetic correspondences in daughter languages
The correlations among the Indo-European languages are for the most part straightforward, but there are some complications with the velar consonants. The languages divide into two groups, known as the centum languages and satem languages, based on the respective words for "hundred" in representative languages of each group (Latin and Avestan, respectively). Each group merges the PIE "plain velars" with one of the other two series, the Centum group merging "palatals" and "plain velars" while the satem group merges labiovelars and "plain velars", removing the labialization in the process. The satem group furthermore converts the "palatal" series into sibilant-type sounds. The following table summarizes the outcomes in the various daughters:



In p-Celtic, Osco-Umbrian, and Aeolian Greek, *kw > /p/. This may be due to contact, perhaps in the Balkan region in the second millennium BC. The same /p/ also occurs in Hittite in a few pronominal forms (pippid "something, someone", cf. Latin quisquid).

=Accent=

Proto-Indo-European accent refers to the accentual system of Proto-Indo-European language.

Description
Proto-Indo-European (PIE) is usually reconstructed as having had variable lexical stress, meaning that the placement of the stress in a word (the accent) was not predictable by phonological rules. Stressed syllables received a higher pitch than unstressed ones; PIE is therefore often said to have had pitch accent – but this must not be confused with the other meaning of the term "pitch accent", which refers to a system where one or two syllables per word have one of at least two unpredictable tones (while the tones of any other syllables are predictable).

PIE accent could be mobile, which means that it could change place throughout the inflectional paradigm. That state of affairs can be seen in Vedic and Ancient Greek, e.g. in the declension of athematic nouns; compare: —or in the conjugation of athematic verbs (compare Sanskrit root present first-person sg. émi, first-person plural imás). Otherwise, the accent was placed at the same syllable throughout the inflection, and according to that placement nouns are divided into barytones accented on the first syllable, and oxytones accented on the last syllable. Compare:
 * PIE 'foot, step' Nom. sg. > Sanskrit , Ancient Greek πούς
 * PIE Gen. sg. *pedés > Sanskrit padás, Ancient Greek ποδός
 * PIE Acc. sg. * > Sanskrit , Ancient Greek πόδᾰ
 * PIE barytone 'wolf' > Sanskrit Nom. sg. vṛ́kas, Gen. sg. vṛ́kasya, Nom. pl. vṛ́kās
 * PIE oxytone *suHnús 'son' > Sanskrit Nom. sg. sūnús, Gen. sg. sūnós, Nom. pl. sūnávas

PIE accent was also free which means that it could stand on any syllable in a word, which is faithfully reflected in Vedic Sanskrit accent (later Classical Sanskrit has predictable accent). Compare:
 * PIE 'carried' > Vedic bháramāṇas
 * PIE 'holds' > Vedic dhāráyati
 * PIE 'worships' > Vedic namasyáti
 * PIE 'red' > Vedic rudhirás

As one can see, the placement of reconstructed PIE accent is reflected in Vedic Sanskrit basically intact. According to the reflex of PIE accent, Indo-European languages are divided into those with free accent preserved (either directly or indirectly), and those with fixed (or bound) accent. Free accent is preserved in Vedic Sanskrit (of modern Indo-Iranian languages, according to some, in Pashto), Ancient Greek, Balto-Slavic and Anatolian. In Proto-Germanic, free accent was retained long enough for Verner's Law to be dependent on it, but later stress was shifted to the first syllable of the word.

Reflexes
Vedic accent is generally considered the most archaic, reflecting fairly faithfully the position of the original PIE accent. Avestan manuscripts do not have written accent, but we know indirectly that in some period free PIE accent was preserved in (e.g. Avestan *r is devoiced yielding -hr- before voiceless stops and after the accent—if the accent was not on the preceding syllable, *r is not devoiced).

Ancient Greek also preserves free PIE accent in its nouns (see Ancient Greek accent), but with limitations that prevent the accent from being positioned farther than the third syllable from the end (next from the end if the last syllable was long). Verbal accent in Greek is almost completely worthless for reconstructing PIE accent, because (other than in a few cases) it is consistently positioned as far to the left as the rules allow.

Proto-Germanic initially preserved PIE free accent, with some innovations. In the last stage of Proto-Germanic, the accent was changed into a stress accent and fixed on the first syllable of the word, but prior to that it left its traces in the operation of Verner's law.

Anatolian languages show traces of old PIE accent in the lengthening of the old accented syllable. Compare:
 * PIE *dóru 'tree; wood' > Hittite, Luwian tāru
 * PIE *wódr̥- 'water' > Hittite wātar, but PIE 'waters' (collective) > Hittite widār

Balto-Slavic also retains free PIE accent. For the reconstruction of Proto-Balto-Slavic accent, the most important is the evidence of Lithuanian, Latvian (traditionally Lithuanian is thought as more relevant, but that role is being increasingly taken over by Latvian), and some Slavic languages, especially West South Slavic languages and their archaic dialects. Balto-Slavic accent is continued in Proto-Slavic accent. Accentual alternations in inflectional paradigms (both verbal and nominal) are also retained in Balto-Slavic. Generally it was held that Balto-Slavic has innovative accentual system, but nowadays, according to some researchers, Balto-Slavic takes a pivotal role in the reconstruction of PIE accent (see below).

Indirect traces of the PIE accent are said to be reflected in the development of certain sounds in various branches. For the most part, however, these are of limited, if any, utility in reconstructing the PIE accent.

Unaccented words
Some PIE lexical categories could be unaccented (clitics). These are chiefly particles (PIE 'and' > Vedic -ca, Latin -que, Ancient Greek τε) and some forms of pronouns (PIE  'to me' > Vedic me).

Vedic Sanskrit evidence also indicates that in some positions Proto-Indo-European verb could be unaccented in some syntactical conditions, such as in finite position in the main clause (but not sentence-initially, where verbs would bear whatever accent they would have borne in subordinate clauses). Same is valid for vocatives, which would be deaccented unless they appeared sentence-initially.

Interpretation
No purely phonological rules for determining the position of PIE accent have been ascertained for now. Nevertheless, according to the traditional doctrine, the following can be said of PIE accentual system: PIE thematic nominals and thematic verbal stems all had fixed accent (i.e. on the same syllable throughout the paradigm), which was inherited in all attested daughter languages. Although, there exist some uncertainties regarding the simple thematic present. Some athematic nominals and verb stems also exhibited fixed accent (chiefly on the root), but most had alternating, mobile accent, exhibiting several characteristical patterns; in all of them the surface accent was to the left in one group of inflected forms (nominoaccusative of nominals, active singular of verbs), and to the right in the rest. These facts are often interpreted as being the result of the interplay between individual morphemes, each of which belonged, unpredictably, to one of several accentual classes in PIE. According to this view, endings and stems could all be underlyingly accented or not, the leftmost underlying accent surfaced, and the words with no underlying accent were accented by default on the leftmost syllable.

Modern theories
Traditionally the PIE accent is reconstructed straightforwardly—by the comparison of Vedic, Ancient Greek and Germanic; e.g. PIE 'father' from Sanskrit pitā́, Ancient Greek πατήρ, Gothic fadar. When the position of accent would match in these languages, that would be the accent reconstructed for "PIE proper". It was taken that the Vedic is the most archaic and the evidence of Vedic would be used to resolve all the potentially problematic cases.

It was shown, however, by Vladislav Illich-Svitych in 1963 that the Balto-Slavic accent does not match with that presupposed PIE accent reconstructed on the basis of Vedic and Ancient Greek—the Greek-Vedic barytones correspond to Balto-Slavic fixed paradigms, and Greek-Vedic oxytones correspond to Balto-Slavic mobile paradigms. Moreover, in about a quarter of all cognate Vedic and Ancient Greek etymons accents do not match at all; e.g.
 * PIE 'field' > Ancient Greek ἀγρός : Vedic ájras
 * PIE 'father-in-law' > Ancient Greek ἑκυρός : Vedic śváśuras
 * PIE 'which' > Ancient Greek πότερος : Vedic katarás

Recently Russian linguists Vladimir Dybo and Sergej Nikolayev have been reconstructing PIE accentual system as a system of two tones: + and − (probably high and low tone). Proto-Indo-European would not thus have, as is usually reconstructed, a system of free accent more or less preserved in Vedic, but instead every morpheme would be inherently high or low (i.e. dominant or recessive, as it cannot be known for sure how those features were phonetically actually manifested), and the position of accent would be later in various daughter languages determined in various ways (depending on the combinations of (+) and (−) morphemes), whereas Vedic would certainly not be the most archaic language. Many correspondences among IE languages, as well as certain phenomena in individual daughters dependent on PIE tones, should corroborate this interpretation.

Dybo lists several shortcomings of the traditional approach to the reconstruction of PIE accent. Amongst others, wrong belief in the direct connection between PIE accent and ablaut which in fact does not actually explain the position of PIE accent at all. Usually, however, it is thought that zero-grade should be unaccented, but that is provably not valid for PIE (e.g. 'wolf',  'seven' etc.) according to the traditional reconstruction. Furthermore, Dybo claims that there is none whatsoever phonological, semantic or morphological reason for the classification of certain word to a certain accentual type, i.e. the traditional model cannot explain why Vedic  'wolf' is barytone and Vedic devás 'deity' is oxytone. According to Dybo, such discrepancies can only be explained by presupposing lexical tone in PIE.