Proto-Indo-European language

The Proto-Indo-European language (PIE) is the reconstructed common ancestor of the Indo-European languages, spoken by the Proto-Indo-Europeans. The existence of such a language has been accepted by linguists for over a century, and reconstruction is far advanced and quite detailed.

Scholars estimate that PIE may have been spoken as a single language (before divergence began) around 3700 BC, though estimates by different authorities can vary by more than a millennium. The most popular hypothesis for the origin and spread of the language is the Kurgan hypothesis, which postulates an origin in the Pontic-Caspian steppe of Eastern Europe and Western Asia. In modern times the existence of the language was first postulated in the 18th century by Sir William Jones, who observed the similarities between Sanskrit, Ancient Greek, and Latin. By the early 1900s well-defined descriptions of PIE had been developed that are still accepted today (with some refinements).

PIE is known 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 sophisticated system of declension and verbs used a similarly sophisticated system of conjugation.

As there is no written evidence of Proto-Indo-European, all knowledge of the language is derived by reconstruction from later languages using linguistic techniques such as the comparative method and the method of internal reconstruction. Relationships to other language families, including the Uralic languages, have been proposed though all such suggestions remain controversial.

Historical and geographical setting
There are several competing hypotheses about when and where PIE was spoken. The Kurgan hypothesis is "the single most popular" model, postulating that the Kurgan culture of the Pontic steppe were the hypothesized speakers of the reconstructed Proto-Indo-European language. Alternative theories such as the Anatolian urheimat and Armenian hypothesis have also gained acceptance.

The satemization process that resulted in the Centum-Satem isogloss probably started as early as the 4th millennium BC and the only thing known for certain is that the proto language must have been differentiated into unconnected daughter dialects by the late 3rd millennium BC.

Mainstream linguistic estimates of the time between PIE and the earliest attested texts (ca. nineteenth century BC; see Kültepe texts) range around 1,500 to 2,500 years, with extreme proposals diverging up to another 100% on either side. Proposed models include:
 * the 4th millennium BC (excluding the Anatolian branch) in Armenia, according to the Armenian hypothesis (proposed in the context of Glottalic theory);
 * the 5th millennium BC (4th excluding the Anatolian branch) in the Pontic-Caspian steppe, according to Marija Gimbutas's Kurgan hypothesis;
 * the 6th millennium BC or later in Northern Europe according to Lothar Kilian's and, especially, Marek Zvelebil's models of a broader homeland;
 * the 6th millennium BC in India, according to Koenraad Elst's Out of India model;
 * the 7th millennium BC in Ariana/BMAC according to a number of scholars.
 * the 7th millennium BC in Anatolia (the 5th, in the Balkans, excluding the Anatolian branch), according to Colin Renfrew's Anatolian hypothesis;
 * the 7th millennium BC in Anatolia (6th excluding the Anatolian branch), according to a 2003 glottochronological study;
 * before the 10th millennium BC in the Paleolithic Continuity Theory.

History
Indo-European studies began with Sir William Jones making and propagating the observation that Sanskrit bore a certain resemblance to classical Greek and Latin. In The Sanscrit Language (1786) he suggested that all three languages had a common root, and that indeed they may all be further related, in turn, to Gothic and the Celtic languages, as well as to Persian.

His third annual discourse before the Asiatic Society on the history and culture of the Hindus (delivered on 2 February 1786 and published in 1788) with the famed "philologer" passage is often cited as the beginning of comparative linguistics and Indo-European studies. This is Jones' most quoted passage, establishing his tremendous find in the history of linguistics:

"The Sanscrit language, whatever be its antiquity, is of a wonderful structure; more perfect than the Greek, more copious than the Latin, and more exquisitely refined than either, yet bearing to both of them a stronger affinity, both in the roots of verbs and the forms of grammar, than could possibly have been produced by accident; so strong indeed, that no philologer could examine them all three, without believing them to have sprung from some common source, which, perhaps, no longer exists; there is a similar reason, though not quite so forcible, for supposing that both the Gothic and the Celtic, though blended with a very different idiom, had the same origin with the Sanscrit; and the old Persian might be added to the same family."

This common source came to be known as Proto-Indo-European.

The classical phase of Indo-European comparative linguistics leads from Franz Bopp's Comparative Grammar (1833) to August Schleicher's 1861 Compendium and up to Karl Brugmann's Grundriss published from the 1880s. Brugmann's junggrammatische re-evaluation of the field and Ferdinand de Saussure's development of the laryngeal theory may be considered the beginning of "contemporary" Indo-European studies.

PIE as described in the early 1900s is still generally accepted today; subsequent work is largely refinement and systematization, as well as the incorporation of new information, notably the Anatolian and Tocharian branches unknown in the 19th century.

Notably, the laryngeal theory, in its early forms discussed since the 1880s, became mainstream after Jerzy Kuryłowicz's 1927 discovery of the survival of at least some of these hypothetical phonemes in Anatolian.

Julius Pokorny's landmark Indogermanisches etymologisches Wörterbuch ("Indo-European Etymological Dictionary", 1959) gave a detailed overview of the lexical knowledge accumulated up until that time, but neglected contemporary trends of morphology and phonology (including the laryngeal theory), and largely ignored Anatolian.

The generation of Indo-Europeanists active in the last third of the 20th century (such as Calvert Watkins, Jochem Schindler and Helmut Rix) developed a better understanding of morphology and, in the wake of Kuryłowicz's 1956 Apophonie, understanding of the ablaut. From the 1960s, knowledge of Anatolian became certain enough to establish its relationship to PIE; see also Indo-Hittite.

Method
There is no direct evidence of PIE, because it was never written. All PIE sounds and words are reconstructed from later Indo-European languages using the comparative method and the method of internal reconstruction. An asterisk is used to mark reconstructed PIE words, such as *' 'water', *' 'dog' (English hound), or * 'three (masculine)'. Many of the words in the modern Indo-European languages seem to have derived from such "protowords" via regular sound changes (e.g., Grimm's law).

As the Proto-Indo-European language broke up, its sound system diverged as well, according to various sound laws in the daughter languages. Notable among these are Grimm's law and Verner's law in Proto-Germanic, loss of prevocalic *p- in Proto-Celtic, reduction to h of prevocalic *s- in Proto-Greek, Brugmann's law and Bartholomae's law in Proto-Indo-Iranian, Grassmann's law independently in both Proto-Greek and Proto-Indo-Iranian, and Winter's law and Hirt's law in Balto-Slavic.

Proposed genetic connections
Many higher-level relationships between Proto-Indo-European and other language families have been proposed, but these hypothesized connections are highly controversial. A proposal often considered to be the most plausible of these is that of an Indo-Uralic family, encompassing PIE and Uralic. The evidence usually cited in favor of this consists in a number of striking morphological and lexical resemblances. Opponents attribute the lexical resemblances to borrowing from Indo-European into Uralic. Frederik Kortlandt, while advocating a connection, concedes that "the gap between Uralic and Indo-European is huge", while Lyle Campbell, an authority on Uralic, denies any relationship exists.

Other proposals, further back in time (and proportionately less accepted), link Indo-European and Uralic with Altaic and the other language families of northern Eurasia, namely Yukaghir, Korean, Japanese, Chukotko-Kamchatkan, Nivkh, Ainu, and Eskimo–Aleut, but excluding Yeniseian (the most comprehensive such proposal is Joseph Greenberg's Eurasiatic), or link Indo-European, Uralic, and Altaic to Afro-Asiatic and Dravidian (the traditional form of the Nostratic hypothesis), and ultimately to a single Proto-Human family.

A more rarely mentioned proposal associates Indo-European with the Northwest Caucasian languages in a family called Proto-Pontic.

Etruscan shows some similarities to Indo-European, such as a genitive in -s. There is no consensus on whether these are due to a genetic relationship, borrowing, chance and sound symbolism, or some combination of these.

Proposed areal connections
The existence of certain PIE typological features in Northwest Caucasian languages may hint at an early Sprachbund or substratum that reached geographically to the PIE homelands. This same type of languages, featuring complex verbs and of which the current Northwest Caucasian languages might have been the sole survivors, was cited by Peter Schrijver to indicate a local lexical and typological reminiscence in western Europe pointing to a possible Neolithic substratum.

Consonants
Alternative notations: The aspirated plosives are sometimes written as ; for the palatals, are often used; and  can replace.

The following are the main characteristics of PIE consonants:
 * PIE had a large number of stops, but few fricatives. The traditional (pre-laryngeal) reconstruction included only one fricative, /s/; however, the modern theory includes three additional fricatives, commonly known as laryngeals and assumed to have been pronounced far back in the mouth (i.e. velar, uvular, and/or glottal).  Laryngeals disappeared from all PIE languages except (to some extent) the Anatolian languages, and as a result the exact pronunciation of the laryngeals is disputed; some linguists have even asserted that /*h₁/ might not have been a fricative at all, but a glottal stop.
 * The number of dorsal consonants has long been a source of contention. The traditional theory, which most linguists still adhere to, calls for three series of back stops, traditionally termed "palatovelar", "plain velar" and "labiovelar" (under an alternative view, plain velar, uvular, and labialized uvular, respectively).  The dispute concerns the status of the traditional plain velar series, which is the least-common series and is most often attested in certain environments; the palatovelar series is not often found in these same environments.  Furthermore, in all, or nearly all, daughters the plain velars have merged into one of the other two series.  This has led some linguists to reconstruct only two series, with the distinction between "palatovelar" and "plain velar" a secondary distinction that arose as an areal feature in some of the daughters.
 * PIE is traditionally reconstructed with three types of voicings for its stops: voiceless, voiced, and breathy-voiced (traditionally termed "voiced aspirated"). This is typologically uncommon (and in fact the original breathy-voiced series has been transformed into other sounds in all but the Indo-Aryan languages); as a result some linguists have proposed the glottalic theory, which proposes a very different reconstruction of these three series.  (This theory, however, is not widely accepted today.)
 * A notable characteristic is that the resonants /r/, /l/, /m/, /n/, /y/ and /w/ could appear as vowels as well as consonants, specifically when not adjacent to another vowel. (The same is usually held to be true of the laryngeals, as well.) This has led to some dispute as to whether PIE should be reconstructed with phonemes /i/ and /u/, or whether these should be considered allophones of /y/ and /w/; however, there is some evidence that /i/, at least, could occur in the same environments as /y/.

Vowels

 * Short vowels:, (and possibly ).
 * Long vowels:, (and possibly ). Sometimes a colon  is employed instead of the macron sign to indicate vowel length (*a:, *e:, *o:).
 * Diphthongs: . Diphthongs are sometimes understood as combinations of a vowel plus a semivowel, e. g. *ey or instead of *ei.
 * Vocalic allophones of laryngeals, nasals, liquids and semivowels:.
 * Long variants of these vocalic allophones may have appeared already in the proto-language by compensatory lengthening (for example of a vowel plus a laryngeal):.

It is often suggested that all and  were earlier derived from an  preceded or followed by, but Mayrhofer, Ringe and a number of others have argued that PIE did in fact have the phoneme  (and possibly also ) independent of.

In fact, Stang's law, a phonological rule active at the Proto-Indo-European stage, produces from older  as the ending of the accusative singular of the stems in  (and possibly  from older  in the respective accusative plural), and therefore compels the assumption that the phoneme  was present in the language.

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). The accent is best preserved in Vedic Sanskrit and (in the case of nouns) Ancient Greek, and indirectly attested in a number of phenomena in other PIE languages.

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 (usually indicated, and often 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 (among different members of a nominal or verbal paradigm) 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 triggered the vocalic allophones of nearby resonants). 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. Originally, morphological categories were distinguished both by ablaut variations and different endings, but the decay of endings has led some languages 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-. Some scholars believe that the inflectional affixes of Indo European reflect ablaut variants, usually zero-grade, of older PIE roots. Often the zero-grade appears where the word's accent has shifted from the root to one of the affixes.

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 mood, 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 dialects 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).

Sample texts
As PIE was spoken by a prehistoric society, no genuine sample texts are available, but since the 19th century modern scholars have made various attempts to compose example texts for purposes of illustration. These texts are educated guesses at best; Calvert Watkins in 1969 observes that in spite of its 150 years' history, comparative linguistics is not in the position to reconstruct a single well-formed sentence in PIE. Nevertheless, such texts do have the merit of giving an impression of what a coherent utterance in PIE might have sounded like.

Published PIE sample texts:
 * Schleicher's fable () by August Schleicher (1868), modernized by Hermann Hirt (1939) and Winfred Lehmann and Ladislav Zgusta (1979)
 * The king and the god () by S. K. Sen, E. P. Hamp et al. (1994)

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-Slavic 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