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Indo-European studies Indo-European studies is a field of linguistics and an interdisciplinary field of study dealing with Indo-European languages, both current and extinct. The goal of those engaged in these studies is to amass information about the hypothetical p ...
, a thematic vowel or theme vowel is the vowel or from
ablaut In linguistics, the Indo-European ablaut (, from German '' Ablaut'' ) is a system of apophony (regular vowel variations) in the Proto-Indo-European language (PIE). An example of ablaut in English is the strong verb ''sing, sang, sung'' and its ...
placed before the ending of a
Proto-Indo-European Proto-Indo-European (PIE) is the reconstructed common ancestor of the Indo-European language family. Its proposed features have been derived by linguistic reconstruction from documented Indo-European languages. No direct record of Proto-Indo ...
(PIE) word. Nouns, adjectives, and verbs in the
Indo-European languages The Indo-European languages are a language family native to the overwhelming majority of Europe, the Iranian plateau, and the northern Indian subcontinent. Some European languages of this family, English, French, Portuguese, Russian, D ...
with this vowel are thematic, and those without it are athematic. Used more generally, a thematic vowel is any vowel found at the end of the
stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...
of a word. Outside Indo-European, the term "thematic vowel" is also used in the grammar of
Kartvelian languages The Kartvelian languages (; ka, ქართველური ენები, tr; also known as South Caucasian, Kartvelic, and Iberian languagesBoeder (2002), p. 3) are a language family indigenous to the South Caucasus and spoken primari ...
(see Georgian verb paradigm for more information on thematic vowels).


Proto-Indo-European

PIE verbs and nominals (nouns and adjectives) consist of three parts: :\underbrace_ The thematic vowel, if present, occurs at the end of the suffix (which may include other vowels or consonants) and before the ending: * 'heat' >
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...
(''thérmos'') * '(he) bears' >
Sanskrit Sanskrit (; attributively , ; nominally , , ) is a classical language belonging to the Indo-Aryan languages, Indo-Aryan branch of the Indo-European languages. It arose in South Asia after its predecessor languages had Trans-cultural diffusion ...
''bhárati'',
Gothic Gothic or Gothics may refer to: People and languages *Goths or Gothic people, the ethnonym of a group of East Germanic tribes **Gothic language, an extinct East Germanic language spoken by the Goths **Crimean Gothic, the Gothic language spoken b ...
Athematic forms, by contrast, have a suffix ending in a consonant, or no suffix at all (or arguably a null suffix): * 'father' > English ''father'' * '(I) am' > English ''am'' For several reasons, athematic forms are thought to be older, and the thematic vowel was likely an innovation of late PIE: Athematic paradigms (
inflection In linguistic morphology, inflection (or inflexion) is a process of word formation in which a word is modified to express different grammatical categories such as tense, case, voice, aspect, person, number, gender, mood, animacy, and ...
patterns) are more "irregular", exhibiting
ablaut In linguistics, the Indo-European ablaut (, from German '' Ablaut'' ) is a system of apophony (regular vowel variations) in the Proto-Indo-European language (PIE). An example of ablaut in English is the strong verb ''sing, sang, sung'' and its ...
and mobile accent, while the thematic paradigms can be seen as a simplification or regularisation of verbal and nominal grammar. In the
Anatolian languages The Anatolian languages are an extinct branch of Indo-European languages that were spoken in Anatolia, part of present-day Turkey. The best known Anatolian language is Hittite, which is considered the earliest-attested Indo-European langua ...
, which were the earliest to split from PIE, thematic verbs are rare or absent. Furthermore, during late PIE and in the older daughter languages, a number of athematic forms were replaced by thematic ones, as in prehistoric Greek *''thes-'' 'god' versus *''thes-o-'' > Classical Greek (''theós''). The thematic vowel technically belongs to the suffix and not the ending, as each suffix is inherently either thematic or athematic. It is also used in some cases to derive stems from roots directly, acting as a suffix in itself (as in the second example above). However, when considering endings which are different for thematic and athematic inflections, it is generally included in the endings as well; see the section on fusion below.


Verbs

In verbs, the thematic vowel is when the following ending begins with a coronal obstruent (, , or ) and otherwise. Here is the present active
indicative A realis mood ( abbreviated ) is a grammatical mood which is used principally to indicate that something is a statement of fact; in other words, to express what the speaker considers to be a known state of affairs, as in declarative sentences. Mos ...
paradigm of 'carry': For comparison, here is an example of an athematic verb, 'to draw'. The plural forms ablaut to zero-grade on the root and shift the accent to the ending: (The first person singular ending is sometimes and sometimes , depending on tense,
voice The human voice consists of sound made by a human being using the vocal tract, including talking, singing, laughing, crying, screaming, shouting, humming or yelling. The human voice frequency is specifically a part of human sound producti ...
and thematicity.)


Origin

The PIE verb is characterized by two distinct sets of endings: one found in the thematic present and the perfect, and another found in the
aorist Aorist (; abbreviated ) verb forms usually express perfective aspect and refer to past events, similar to a preterite. Ancient Greek grammar had the aorist form, and the grammars of other Indo-European languages and languages influenced by th ...
and the athematic present. The middle endings seem like a mixture of these two. The thematic conjugation was widespread in what
Donald Ringe Donald "Don" Ringe () is an American linguist and Indo-Europeanist. Ringe graduated from University of Kentucky and then received a Master of Philosophy in Linguistics as a Marshall Scholar from the University of Oxford. He received Ph.D in l ...
terms "Western Indo-European" (Western IE), i.e. IE excluding Tocharian and especially Anatolian. The biggest problem on the origin of PIE thematic inflection is that the thematic endings have more in common with the PIE perfect (which formally, though not functionally and lexically, corresponds to the ''ḫi''-conjugation in Hittite and other Anatolian languages), and that the actual etymological cognates reconstructed of thematic presents are few among the verbs belonging to the Anatolian ''ḫi''-conjugation. In fact, most of the verbs belonging to the ''ḫi''-conjugation in Anatolian actually have lexical cognates that inflect as ''athematic'' verbs in Western IE. All types of verbs belonging to the ''ḫi''-conjugation in Hittite can be shown to have, or to originally have had the
ablaut In linguistics, the Indo-European ablaut (, from German '' Ablaut'' ) is a system of apophony (regular vowel variations) in the Proto-Indo-European language (PIE). An example of ablaut in English is the strong verb ''sing, sang, sung'' and its ...
pattern with in the singular and the zero-grade in the plural, which is exactly the pattern of the Western PIE perfect. The thematic presents in Western PIE also do not have quantitative ablaut, which indicates their relatively recent origin. This all has caused some linguists to speculate that perfect and thematic present endings go back to a single Early PIE prototype. According to Matasović, the Early PIE stative (becoming the perfect) is responsible for the original form of the thematic suffix , while the e-grade form is secondary. Verbs forming the underived thematic presents are overwhelmingly bivalent/transitive, and there are no statives in the Late PIE thematic inflection since all the original Early PIE statives either remained athematic presents, or they became Western PIE perfects. It is also probable that some Early PIE middle verbs also became thematic in the Western PIE period, since they lack middle correspondences in Anatolian.


Nouns

In nouns, the thematic vowel is almost always , and only becomes when there is no ending or when followed by in the neuter nominative/accusative plural. Here is an example paradigm for 'bear', a thematic
animate Animation is a method by which still figures are manipulated to appear as moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Today, most anim ...
noun, supplemented by the neuter 'plough' for the nominative/accusative: Again, athematic nouns show ablaut and accent shifts, mainly between the "strong" cases (nominative and vocative in all numbers, and accusative singular/dual) and the "weak" cases (all others). A few endings are also different from the thematic paradigm; for example, the nominative/accusative neuter has instead of . See Athematic accent/ablaut classes of PIE nouns for examples.


Origin

There are several theories about the rise of ''o''-stems in PIE nominal inflection. Two are the most prominent: * ''o''-stems reflect an ergative system that existed in the prehistory of PIE, and * ''o''-stems arise from pronouns.


=Ergative theory

=
Pedersen Pedersen () is a Danish and Norwegian patronymic surname, literally meaning "son of Peder". It is the fourth most common surname in Denmark, shared by about 3.4% of the population, and the sixth most common in Norway. It is of similar origin as the ...
was the first to notice that the subject of the
transitive verb A transitive verb is a verb that accepts one or more objects, for example, 'cleaned' in ''Donald cleaned the window''. This contrasts with intransitive verbs, which do not have objects, for example, 'panicked' in ''Donald panicked''. Transiti ...
looked as if it had the form of the
genitive In grammar, the genitive case ( abbreviated ) is the grammatical case that marks a word, usually a noun, as modifying another word, also usually a noun—thus indicating an attributive relationship of one noun to the other noun. A genitive can a ...
(a '' sigmatic'' case) if it were
active Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * Active Records, a record label Ships * ''Active'' (ship), several commercial ships by that name * HMS ''Active'', the name of various ships of the British Royal ...
, and as if it had the form of the
instrumental case In grammar, the instrumental case ( abbreviated or ) is a grammatical case used to indicate that a noun is the ''instrument'' or means by or with which the subject achieves or accomplishes an action. The noun may be either a physical object or a ...
if it were inactive. Furthermore, the subject and object of intransitive verbs seemed to have the form of the absolutive (i.e. an ''asigmatic'' case). This caused an asymmetry between the valencies of transitive and intransitive verbs, summarized in the table below: This theory was further developed by Beekes and Kortlandt, who assumed that the nominative syntax of old Indo-European languages was formed later and that the case system of the PIE language was primarily based on the ergative syntax. The same ending shared by the nominative and accusative neuter, originally designating inactive nouns, originated from the originally absolutive case, while the ergative was used with the active subject. Beekes claims the sigmatic genitive-ablative developed from the ergative. After the transformation of the ergative system into the nominative system, the form reconstructed as became the nominative, a new case of subject. Later what was to become the thematic vowel spread to other cases as well, giving rise to ''o''-stem inflection. Similar theories that assume the ergative past of the PIE syntax have been formulated by Gamkrelidze and
Ivanov Ivanov, Ivanoff or Ivanow (masculine, bg, Иванов, russian: ИвановSometimes the stress is on Ива́нов in Bulgarian if it is a middle name, or in Russian as a rare variant of pronunciation), or Ivanova (feminine, bg, Иванов ...
and Schmalstieg. A related theory that also derives the thematic conjugation from an oblique case form was proposed by Ranko Matasović, who, however, identified the source form as the genitive. Matasović argued that the thematic o-stem nouns were the result of the nominalisation of adjectives, which in turn arose through the reinterpretation as nominative forms of original (attributively used) genitives of athematic (mostly deverbal) root-nouns. For example, the stem *''(h)yug-o'' (cf. Latin iugum'') was abstracted from *''(H)yug-os'', which was originally a genitive of a root noun *''(H)yewg-s'' (cf. Latin ''coniūx'').Thus, a phrase like ''*ukwsōn yug-os'' 'ox of yoking' was reinterpreted as 'yoked ox'. This theory, like the previous one, would explain why there is much evidence in favour of original syncretism of the nominative and genitive singular in the o-stems.


=Pronominal theory

= According to
Jean Haudry Jean Haudry (born 28 May 1934) is a French linguist and Indo-Europeanist. Haudry is generally regarded as a distinguished linguist by other scholars, although he has also been criticized for his political proximity with the far-right. Haudry's '' ...
''o''-stems originated from pronouns with a determining function that were suffixed to a nominal base, playing the role of a postpositional article. There exists a number of typological parallels for such a development: * in
Balto-Slavic The Balto-Slavic languages form a branch of the Indo-European family of languages, traditionally comprising the Baltic and Slavic languages. Baltic and Slavic languages share several linguistic traits not found in any other Indo-European br ...
, where definite adjectives are formed by suffixing the PIE relative pronoun . * modern Balkanian and
Scandinavian languages The North Germanic languages make up one of the three branches of the Germanic languages—a sub-family of the Indo-European languages—along with the West Germanic languages and the extinct East Germanic languages. The language group is als ...
, which developed postpositional determination using demonstratives *
mimation Mimation refers to the suffixed '  (the letter mem in many Semitic abjads) which occurs in some Semitic languages. This occurs in Akkadian on singular nouns.nunation Nunation ( ar, تَنوِين, ' ), in some Semitic languages such as Literary Arabic, is the addition of one of three vowel diacritics (''ḥarakāt'') to a noun or adjective. This is used to indicate the word ends in an alveolar nasal without ...
in
Semitic languages The Semitic languages are a branch of the Afroasiatic language family. They are spoken by more than 330 million people across much of West Asia, the Horn of Africa, and latterly North Africa, Malta, West Africa, Chad, and in large immigrant ...
.


Developments from thematic and athematic paradigms

Thematic and athematic forms were passed on to the daughter languages of Proto-Indo-European. In the most ancient languages, such as Sanskrit and Ancient Greek, the distinction between athematic and thematic nouns and verbs is preserved. In later languages, the thematic versus athematic distinction in nouns was replaced by distinctions between various thematic ("vowel") and athematic ("consonant") declensions, and athematic verbs are typically regarded as irregular. As a consequence of such language changes, the distribution of thematic and athematic words differs widely in Indo-European languages.
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
, for example, has only very few athematic verbs, while Sanskrit preserves a large number of these. Greek resembles both Sanskrit and Latin in different respects.


Fusion

Even in ancient languages, the thematic vowel is often indistinguishable from the case ending, because the two have fused together: *
Old Latin Old Latin, also known as Early Latin or Archaic Latin (Classical la, prīsca Latīnitās, lit=ancient Latinity), was the Latin language in the period before 75 BC, i.e. before the age of Classical Latin. It descends from a common Proto-Italic ...
''sax-o-is'' > Classical Latin ''sax-īs'', dative plural of ''sax-u-m'' (Old Latin ''sax-o-m'') 'stone' *
Homeric Homer (; grc, Ὅμηρος , ''Hómēros'') (born ) was a Greek poet who is credited as the author of the ''Iliad'' and the ''Odyssey'', two epic poems that are foundational works of ancient Greek literature. Homer is considered one of the ...
(''the-ā́-ōn'') > Attic (''the-ôn''), genitive plural of (''the-ā́'') 'goddess' In Latin, athematic verbs were lost, except for a few, which were considered irregular or adopted into one of the four thematic conjugations: * ''s-um, es, es-t, s-umus, es-tis, s-unt'' (irregular) 'be' * (''ferō'',) ''fer-s, fer-t'', (ferimus,) ''fer-tis, fer-unt'' (irregular) 'carry' * (''dō'',) ''dā-s, da-t, da-mus, da-tis, da-nt'' (first conjugation) 'give'


Thematic ''a''

Although the ''a'' of the Greek and Latin first declension was not originally a thematic vowel, it is considered one in Greek and Latin grammar. In both languages, first-declension nouns take some endings belonging to the thematic
second declension The second declension is a category of nouns in Latin and Greek with similar case formation. In particular, these nouns are thematic, with an original ''o'' in most of their forms. In Classical Latin, the short ''o'' of the nominative and accusativ ...
. An a-stem noun was originally a
collective noun In linguistics, a collective noun is a word referring to a collection of things taken as a whole. Most collective nouns in everyday speech are not specific to one kind of thing. For example, the collective noun "group" can be applied to people (" ...
suffixed with , the ending of the neuter plural. * (no case ending) > Latin ''barba'' 'beard'


Athematic vowels

Sometimes vowels near the end of a noun or verb, where one would expect a thematic vowel, are not actually thematic vowels. Either these vowels are placed after an ''e'' or ''o'', or they are on their own. In both Latin and Greek, there are athematic nouns whose stems end in ''i'' or ''u'' (with the
allophone In phonology, an allophone (; from the Greek , , 'other' and , , 'voice, sound') is a set of multiple possible spoken soundsor ''phones''or signs used to pronounce a single phoneme in a particular language. For example, in English, (as in '' ...
s ''y'' or ''w'' before vowels). These include Latin ''nāvis'' 'ship' and Greek ''thesis'' 'placement'; Latin ''senātus'' 'council of elders' or 'senate' and Greek ''basileus'' 'king'. Because these vowels are not ''e'' or ''o'', they are not thematic, and the nouns take the same endings as consonant-stem nouns. * Latin ''nāvi-s'', ''senātu-s'' · ''rēg-s'' 'king' * Greek ''thesi-s'', ''basileu-s'' · ''Arab-s'' (''Araps'') 'Arab' In Latin, there are four conjugations depending on the vowel before the endings (which include the thematic vowel): a, e, none, i. Although all the verbs belonging to these conjugations are thematic, these four vowels are not the thematic vowel of the different declensions: the thematic vowel is an ''e/o'' that has either fused with the endings and conjugation vowel or changed to ''i/u''. In Greek, some of the Latin conjugations are represented by contracted verbs instead, in which the stem vowel
contracts A contract is a legally enforceable agreement between two or more parties that creates, defines, and governs mutual rights and obligations between them. A contract typically involves the transfer of goods, services, money, or a promise to tr ...
with the ending (which includes the thematic vowel). This results in different vowels in the ending from the non-contracted verbs. * ''tīmaeis'' > ''tīmāis'' 'you honor'


Individual languages


Latin

In Latin, nouns of the first, second, fourth, and fifth declensions are considered thematic; the first declension has the theme vowel ''a'', the second ''o'', the fourth ''u'', and the fifth ''e''. Stems with ''i'' are treated together with athematic stems in the third declension, as they came to closely resemble one another. Latin verbs are subject to a similar classification: the first
conjugation Conjugation or conjugate may refer to: Linguistics *Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics *Complex conjugation, the change ...
contains vowel stems with ''a'', the second with ''e'', and the fourth with ''i''. There are no Latin verbs with ''o'' or ''u'', and very few are athematic, but they are considered
irregular verb A regular verb is any verb whose conjugation follows the typical pattern, or one of the typical patterns, of the language to which it belongs. A verb whose conjugation follows a different pattern is called an irregular verb. This is one instanc ...
s. For example, consider the noun endings of the Latin "first declension" singular of the word ''rosa'' 'rose': The vowel ''a'' is prominent in these case endings, so nouns like ''rosa'' came to be known as "a-stem" nouns, with ''a'' being the "theme vowel," and such a word was later analysed as having a stem containing a root plus a
suffix In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns, adjectives, and verb endings, which form the conjugation of verbs. Suffixes can carr ...
. In fact,
philologists Philology () is the study of language in oral and written historical sources; it is the intersection of textual criticism, literary criticism, history, and linguistics (with especially strong ties to etymology). Philology is also defined ...
now believe that the suffix in PIE was , with a laryngeal that usually became ''a'' in the daughter languages.


Sanskrit

Sanskrit grammar ordains a ''vikaraṇapratyaya'' (modificatory affix) between a verbal root and the tense-ending. Thematic verbal roots are those with an ''-a'' in the vikaraṇapratyaya, to wit, roots belonging to the 1st, 4th, 6th and 10th conjugation classes. Among nominals, those with the ''prātipadika'' (stem) ending in ''-a'' would the thematic nominals by this definition.


Ancient Greek


Verbs

The distinction between thematic and athematic stems is especially apparent in the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
verb A verb () is a word ( part of speech) that in syntax generally conveys an action (''bring'', ''read'', ''walk'', ''run'', ''learn''), an occurrence (''happen'', ''become''), or a state of being (''be'', ''exist'', ''stand''). In the usual descr ...
; they fall into two classes that are marked by quite different personal endings. Thematic verbs are also called -ω (-''ō'') verbs in Greek; athematic verbs are -μι (-''mi'') verbs, after the
first person singular In linguistics, grammatical person is the grammatical distinction between deictic references to participant(s) in an event; typically the distinction is between the speaker ( first person), the addressee ( second person), and others (third pers ...
present tense The present tense ( abbreviated or ) is a grammatical tense whose principal function is to locate a situation or event in the present time. The present tense is used for actions which are happening now. In order to explain and understand present ...
ending that each of them uses. The entire
conjugation Conjugation or conjugate may refer to: Linguistics *Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics *Complex conjugation, the change ...
seems to differ quite markedly between the two sets of verbs, but the differences are really the result of the thematic vowel reacting (fusing) with the verb endings, apart from the first person singular which already had different endings for thematic and athematic verbs in PIE. In classical Greek, the present tense active endings for athematic verbs are: :-μι, -ς, σι, -μεν, -τε, -ασι(ν) :(''-mi, -s, -si, -men, -te, -asi(n)'') while the thematic verbs took the endings: :-ω, -εις, -ει, -ομεν, -ετε, -ουσι(ν) :(''-ō, -eis, -ei, -omen, -ete, -ousi(n)'') In Greek, athematic verbs, except for those that end in -νῡμι -''nūmi'', are a
closed class In grammar, a part of speech or part-of-speech ( abbreviated as POS or PoS, also known as word class or grammatical category) is a category of words (or, more generally, of lexical items) that have similar grammatical properties. Words that are ass ...
of inherited forms from PIE.


Nouns

Greek preserves thematic nouns in the first (or alpha) declension and second (or omicron) declension, and athematic nouns in the
third declension {{No footnotes, date=February 2021 The third declension is a category of nouns in Latin and Greek with broadly similar case formation — diverse stems, but similar endings. Sanskrit also has a corresponding class (although not commonly ter ...
. Declension of the athematic noun (''poús'') 'foot': Declension of the thematic noun (''ánthropos'') 'man':


Other languages

Most other Indo-European languages have similar distinctions, or had them in their past. Marked contrasts between thematic and athematic verbs appear in Lithuanian, and
Old Church Slavonic Old Church Slavonic or Old Slavonic () was the first Slavic literary language. Historians credit the 9th-century Byzantine missionaries Saints Cyril and Methodius with standardizing the language and using it in translating the Bible and othe ...
. In the Germanic and
Insular Celtic languages Insular Celtic languages are the group of Celtic languages of Brittany, Great Britain, Ireland, and the Isle of Man. All surviving Celtic languages are in the Insular group, including Breton, which is spoken on continental Europe in Brittany ...
, the theme vowels are often hard to perceive because of the loss of final vowels. However, their presence is still felt, in a manner that defines different ways of declining nouns or conjugating verbs, so
philologists Philology () is the study of language in oral and written historical sources; it is the intersection of textual criticism, literary criticism, history, and linguistics (with especially strong ties to etymology). Philology is also defined ...
still occasionally speak of vowel stems and consonant stems in these languages as well. While
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlers in the mid-5th ...
still contrasted "vowel stems" (thematic) and "consonant stems" (athematic), this distinction is no longer a meaningful one in Modern English, as in other languages whose morphology has been drastically simplified by
analogy Analogy (from Greek ''analogia'', "proportion", from ''ana-'' "upon, according to" lso "against", "anew"+ ''logos'' "ratio" lso "word, speech, reckoning" is a cognitive process of transferring information or meaning from a particular subject ...
.


Etymology

In the term ''thematic vowel'', ''theme'' refers to the stem of a word. For example, in the Ancient Greek verb (''témnō'') 'cut', ''tem-'' is the root, and ''temn-'' is the stem or theme for the
present tense The present tense ( abbreviated or ) is a grammatical tense whose principal function is to locate a situation or event in the present time. The present tense is used for actions which are happening now. In order to explain and understand present ...
. Hence, ''thematic vowel'' loosely means "stem vowel".


Notes


References

* * (U.S.) * * * * * Matthias Fritz, Michael Meier-Brügger: ''Indogermanische Sprachwissenschaft.'' Walter de Gruyter, Berlin 2021 (10., völlig neu bearbeitete Auflage), ISBN 978-3-11-059832-2 * * * {{Proto-Indo-European language Indo-European linguistics de:Indogermanische Ursprache#Themavokal