Laryngeal theory


The laryngeal theory is a widely accepted hypothesis in the historical linguistics of the Indo-European languages positing that:
The theory aims to:
In its earlier form, the theory proposed two sounds in PIE. Combined with a reconstructed *e or *o, the sounds produce vowel phonemes that would not otherwise be predicted by the rules of ablaut. The theory received considerable support after the decipherment of Hittite, which revealed it to be an Indo-European language.
Many Hittite words were shown to be derived from PIE, with a phoneme represented as ḫ corresponding to one of the hypothetical PIE sounds. Subsequent scholarship has established a set of rules by which an ever-increasing number of reflexes in daughter languages may be derived from PIE roots. The number of explanations thus achieved and the simplicity of the postulated system have both led to widespread acceptance of the theory.
In its most widely accepted version, the theory posits three phonemes in PIE: h₁, h₂, and h₃. Other daughter languages inherited the derived sounds, resulting from their merger with PIE short vowels and their subsequent loss.
The phonemes are now recognized as consonants, related to articulation in the general area of the larynx, where a consonantal gesture may affect vowel quality. They are regularly known as laryngeal, but the actual place of articulation for each consonant remains a matter of debate..
The laryngeals got their name because they were believed by Hermann Möller and Albert Cuny to have had a pharyngeal, epiglottal, or glottal place of articulation, involving a constriction near the larynx. While this is still possible, many linguists now think of "laryngeals", or some of them, as having been velar or uvular.
The evidence for their existence is mostly indirect, as will be shown below, but the theory serves as an elegant explanation for several properties of the PIE vowel system that made no sense until the theory, such as the "independent" schwas. Also, the hypothesis that PIE schwa *ə was a consonant, not a vowel, provides an elegant explanation for some apparent exceptions to Brugmann's law in Indic languages.

History

The beginnings of the theory were proposed by Ferdinand de Saussure in 1879, in an article chiefly devoted to something else altogether.
In the course of his analysis, Saussure proposed that what had then been reconstructed as long vowels *ā and *ō, alternating with *ǝ, was an ordinary type of PIE ablaut. That is, it was an alternation between e-grade and zero grade like in "regular" ablaut, but followed by a previously unidentified element. This "element" accounted for both the changed vowel colour and the lengthening.
So, rather than reconstructing *ā, *ō and *ǝ as others had done before, Saussure proposed something like *eA alternating with *A and *eO with *O, where A and O represented the unidentified elements. Saussure called them simply "coefficients sonantiques", which was the term for what are now in English more usually called resonants; that is, the six elements present in PIE which can be either consonants or vowels depending on the sounds they are adjacent to: *y w r l m n.
These views were accepted by a few scholars, in particular Hermann Möller, who added important elements to the theory. Saussure's observations, however, did not achieve any general currency, as they were still too abstract and had little direct evidence to back them up.
This changed when Hittite was discovered and deciphered in the early 20th century. Hittite phonology included two sounds written with symbols from the Akkadian syllabary conventionally transcribed as ', as in ' "I put, am putting". This consonant did not appear to be related to any of the consonants then reconstructed for PIE, and various unsatisfactory proposals were made to explain this consonant in terms of the PIE consonant system as it had then been reconstructed.
It remained for Jerzy Kuryłowicz to propose that these sounds lined up with Saussure's conjectures. He suggested that the unknown consonant of Hittite was, in fact, a direct reflex of the coefficients sonantiques that Saussure had proposed.
Their appearance explained some other matters as well: For example, why verb roots containing only a consonant and a vowel always have long vowels. For example, in *dō- "give", the new consonants allowed linguists to decompose this further into *deh₃. This not only accounted for the patterns of alternation more economically than before but also brought the structure of these roots into line with the basic PIE pattern which required roots to begin and end with a consonant.
The lateness of the discovery of these sounds by Indo-Europeanists is largely because Hittite and the other Anatolian languages are the only Indo-European languages for which at least some are attested directly and consistently as consonantal sounds. Otherwise, their presence is to be inferred mostly through the effects they have on neighboring sounds, and on patterns of alternation that they participate in. When a laryngeal is attested directly, it is usually as a special type of vowel and not as a consonant, best exemplified in Greek where syllabic laryngeals developed as such: *h₁ > e, *h₂ > a, and *h₃ > o.

Varieties of laryngeals

There are many variations of the laryngeal theory. Some scholars, such as Oswald Szemerényi, reconstruct just one laryngeal. Some follow Jaan Puhvel's reconstruction of eight or more.

Basic Laryngeal Set

Most scholars work with a basic three:
Some scholars suggest the existence of a fourth consonant,, which differs from in not being reflected as Anatolian but being reflected, to the exclusion of all other laryngeals, as Albanian h when word-initial before an originally stressed vowel.
E.g. PIE *h₄órǵʰiyeh₂ "testicle" yields Albanian herdhe "testicle" but Hittite arki- "testicle" whereas PIE "bear" yields Alb. ari "bear" but Hittite hartga- "cultic official, bear-person".
When there is an uncertainty whether the laryngeal is or, the symbol may be used.
Another such theory, but much less generally accepted, is Winfred P. Lehmann's view, based on inconsistent reflexes in Hittite, that was two separate sounds.

Direct evidence for laryngeals

Some direct evidence for laryngeal consonants comes from Anatolian:
PIE *a is a fairly rare sound, and in an uncommonly large number of good etymologies, it is word-initial. Thus PIE *anti "in front of and facing" > Greek antí "against"; Latin ante "in front of, before"; Sanskrit ánti "near; in the presence of". But in Hittite there is a noun ' "front, face", with various derivatives, pointing to a PIE root-noun "face".
Similarly, the traditional PIE reconstruction for 'sheep' is *owi- whence Sanskrit '-, Latin ', Greek '. But Luwian has -, indicating instead a reconstruction.

Pronunciation

Considerable debate still surrounds the pronunciation of the laryngeals and various arguments have been given to pinpoint their exact place of articulation. Firstly the effect these sounds have had on adjacent phonemes is well documented. The evidence from Hittite and Uralic is sufficient to conclude that these sounds were "guttural" or pronounced rather back in the vocal tract. The same evidence is also consistent with the assumption that they were fricative sounds, an assumption that is strongly supported by the behaviour of laryngeals in consonant clusters.

*h₁

suggested a consonantal realization for *h₁ as the voiceless glottal fricative with a syllabic allophone . This is supported by the closeness of to , its failure to create an auxiliary vowel in Greek and Tocharian when it occurs between a semivowel and a consonant, and the typological likelihood of an given the presence of aspirated consonants in PIE.
It has been suggested by Beekes that *h₁ is a glottal stop. However, Winfred P. Lehmann instead theorized, based on inconsistent reflexes in Hittite, that there were two *h₁ sounds: a glottal stop and an h sound as in English hat.
In 2004, Alwin Kloekhorst argued that the Hieroglyphic Luwian sign no. 19 stood for /ʔa/ and represents the reflex of ; this would support the hypothesis that, or at least some cases of it, was. Later, Kloekhorst claimed that also Hittite preserves PIE *h₁ as a glottal stop, visible in words like Hittite e-eš-zi 'he is' < PIE *h₁és-ti, where an extra initial vowel sign is used. This hypothesis has met with serious criticism
Recently, however, Simon has supported Kloekhorst's thesis by suggesting that plene spelling in Cuneiform Luwian can be explained in a similar way. Additionally, Simon's article revises the Hieroglyphic Luwian evidence and concludes that "although some details of Kloekhorst's arguments could not be maintained, his theory can be confirmed."
An occasionally idea is advanced that the laryngeals were dorsal fricatives corresponding directly to the three traditionally reconstructed series of dorsal stops suggests a further possibility, a palatal fricative.

*h₂

From what is known of such phonetic conditioning in contemporary languages, notably Semitic languages, *h₂ could have been a pharyngeal fricative such as and. Pharyngeal consonants often cause a-colouring in the Semitic languages. Uvular fricatives, however, may also colour vowels, thus is also a noteworthy candidate. Weiss suggests that this was the case in Proto-Indo-European proper, and that a shift from uvular into pharyngeal may have been a common innovation of the non-Anatolian languages. Rasmussen suggested a consonantal realization for *h₂ as a voiceless velar fricative, with a syllabic allophone, i.e. a near-open central vowel.

*h₃

Likewise it is generally assumed that *h₃ was rounded due to its o-colouring effects. It is often taken to have been voiced based on the perfect form *pi-bh₃- from the root *peh₃ "drink". Rasmussen has chosen a consonantal realization for *h₃ as a voiced labialized velar fricative, with a syllabic allophone, i.e. a close-mid central rounded vowel. Kümmel instead suggests.

Support for theory from daughter languages

The hypothetical existence of laryngeals in PIE finds support in the body of daughter language cognates which can be most efficiently explained through simple rules of development.

Direct reflexes of laryngeals

Unambiguous examples are confined to Anatolian languages. Words with Hittite ḫ, Luwian h and Lycian x are explained as reflexes of PIE roots with h₂.
Some Hittitologists have also proposed that "h₃" was preserved in Hittite as "ḫ", although only word initially and after a resonant. Kortlandt holds that "h₃" was preserved before all vowels except "*o". Similarly, Kloekhorst believes they were lost before resonants as well.

In Germanic

Reconstructed instances of *kw in Proto-Germanic have been explained as reflexes of PIE *h₃w, a process known as Cowgill's law. The proposal has been challenged but is defended by Don Ringe.

In Albanian

In the Albanian language, a minority view proposes that some instances of word-initial h continue a laryngeal consonant.

In Western Iranian

Martin Kümmel has proposed that some initial and in contemporary Western Iranian languages, commonly thought to be prothetic, are instead direct survivals of *h₂, lost in epigraphic Old Persian but retained in "marginal dialects" ancestral among others to Modern Persian.

Proposed indirect reflexes

In all other daughter languages, a comparison of the cognates can support only hypothetical intermediary sounds derived from PIE combinations of vowels and laryngeals. Some indirect reflexes are required to support the examples above where the existence of laryngeals is uncontested.
The proposals in this table account only for attested forms in daughter languages. Extensive scholarship has produced a large body of cognates which may be identified as reflexes of a small set of hypothetical intermediary sounds, including those in the table above. Individual sets of cognates are explicable by other hypotheses but the sheer bulk of data and the elegance of the laryngeal explanation have led to widespread acceptance in principle.

Vowel coloration and lengthening

In the proposed Anatolian-language reflexes above, only some of the vowel sounds reflect PIE *e. In the daughter languages in general, many vowel sounds are not obvious reflexes. The theory explains this as the result of
The results of H-coloration and H-loss are recognized in daughter-language reflexes such as those in the table below

Greek triple reflex vs schwa

Between three phonological contexts, Greek reflexes display a regular vowel pattern that is absent from the supposed cognates in other daughter languages.
Before the development of laryngeal theory, scholars compared Greek, Latin and Sanskrit and concluded the existence in these contexts of a schwa vowel in PIE, the so-called schwa indogermanicum. The contexts are: 1. between consonants ; 2. word initial before a consonant ; 3. combined with a liquid or nasal consonant .
Laryngeal theory provides a more elegant general description than reconstructed schwa by assuming that the Greek vowels are derived through vowel colouring and H-loss from PIE h₁, h₂, h₃, constituting a so-called triple reflex.
The phonology of the sonorant examples in the previous table can only be explained by the presence of an adjacent phonemes in PIE. Assuming the phonemes to be a following h₁, h₂ or h₃ allows the same rules of vowel coloration and H-loss to apply to both PIE *e and PIE sonorants.

Support from Greek ablaut

The hypothetical values for sounds with laryngeals after H-coloration and H-loss draw much of their support for the regularization they allow in ablaut patterns, specifically the uncontested patterns found in Greek.
Ablaut in the root
In the following table, each row shows undisputed Greek cognates sharing the three ablaut grades of a root. The four sonorants and the two semi-vowel are represented as individual letters, other consonants as C and the vowel or its absence as.
The reconstructed PIE e-grade and zero-grade of the above roots may be arranged as follows:
An extension of the table to PIE roots ending in presumed laryngeals allows many Greek cognates to follow a regular ablaut pattern.
Ablaut in the suffix
The first row of the following table shows how uncontested cognates relate to reconstructed PIE stems with e-grade or zero-grade roots, followed by e-grade or zero-grade of the suffix –w-. The remaining rows show how the ablaut pattern of other cognates is preserved if the stems are presumed to include the suffixes h₁, h₂, h₃.

Intervocalic H-loss

In the preceding sections, forms in the daughter languages were explained as reflexes of laryngeals in PIE stems. Since these stems are judged to have contained only one vowel, the explanations involved H-loss either when a vowel preceded or when a vowel followed. However, the possibility of H-loss between two vowels is present when a stem combines with an inflexional suffix.
It has been proposed that PIE H-loss resulted in hiatus, which in turn was contracted to a vowel sound distinct from other long vowels by being disyllabic or of extra length.
Early Indo-Iranian disyllables
A number of long vowels in Avestan were pronounced as two syllables, and some examples also exist in early Sanskrit, particularly in the Rig Veda. These can be explained as reflexes of contraction following a hiatus caused by the loss of intervocalic H in PIE.
Proto-Germanic trimoric o
The reconstructed phonology of Proto-Germanic, the presumed ancestor of the Germanic languages, includes a long *ō phoneme, which is in turn the reflex of PIE ā. As outlined above Laryngeal theory has identified instances of PIE ā as reflexes of earlier *h₂e, *eh₂ or *aH before a consonant.
However, a distinct long P-Gmc *ō phoneme has been recognized with a different set of reflexes in daughter Germanic languages. The vowel length has been calculated by observing the effect of the shortening of final vowels in Gothic.
Reflexes of trimoric or overlong *ô are found in the final syllable of nouns or verbs, and are thus associated with inflectional endings. Thus four P-Gmc sounds are proposed, shown here with Gothic and Old English reflexes:
A somewhat different contrast is observed in endings with final *z:
Laryngeal theory preserves regularities in declensions and conjugations by explaining the trimoric sound as a reflex of H-loss between vowels followed by contraction. Thus
The reconstructed phonology of the Balto-Slavic languages posits two distinct long vowels in almost exact correspondence to bimoric and trimoric vowels in Proto-Germanic. The Balto-Slavic vowels are distinguished not by length but by intonation; long vowels with circumflex accent correspond to P-Gmc trimoric vowels. A significant proportion of long vowels with an acute accent correspond to P-Gmc bimoric vowels. These correspondences have led to the suggestion that the split between them occurred in the last common ancestor of the two daughters.
It has been suggested that acute intonation was associated with glottalization, a suggestion supported by glottalized reflexes in Latvian. This could lend support to a theory that laryngeal consonants developed into glottal stops before their disappearance in Balto-Slavic and Proto-Germanic.

H-loss adjacent to other sounds

After stop consonants
A significant number of instances of voiceless aspirates in the Indo-Iranian languages may be explained as reflexes of PIE stop consonants immediately followed by laryngeals..
After resonants
PIE resonants *r̥,*l̥,*m̥,*n̥ are predicted to become consonantal allophones *r, *l*, *m, *n* when immediately followed by a vowel. Using R to symbolize any resonant and V for any vowel, *R̥V>*RV. Instances in the daughter languages of a vocalic resonant immediately followed by a vowel are explained as reflexes of PIE *R̥HV with a laryngeal between the resonant and the vowel giving rise to a vocalic allophone. This original vocalic quality was preserved following H-loss.
Next to semi-vowels
Laryngeal theory has been used to explain the occurrence of a reconstructed sound change is known as Holtzmann's law or sharpening in North Germanic and East Germanic languages. The existing theory explains that PIE semivowels *y and *w were doubled to P-Gmc *-yy- and *-ww-, and that these in turn became -ddj-and -ggw-respectively in Gothic and -ggj- and -ggw- in early North Germanic languages. However, the existing theory had difficulty in predicting which instances of PIE semivowels led to sharpening and which instances failed to do so. The new explanation proposes that words exhibiting sharpening are derived from PIE words with laryngeals.
Old Norse tryggr*drewh₂yo
'trustworthy'*trewwjazwithout sharpening*triuwjazOld English trēowe
Old High German gitriuwi
Many of these techniques rely on the laryngeal being preceded by a vowel, and so they are not readily applicable for word-initial laryngeals except in Greek and Armenian. However, occasionally languages have compounds in which a medial vowel is unexpectedly lengthened or otherwise shows the effect of the following laryngeal. This shows that the second word originally began with a laryngeal and that this laryngeal still existed at the time the compound was formed.

Laryngeals in the Uralic languages

Further evidence of the laryngeals has been found in Uralic languages. While Proto-Uralic and PIE have not been demonstrated to be genetically related, some word correspondences between Uralic and Indo-European have been identified as likely borrowings from very early Indo-European dialects to early Uralic dialects. One example is the widespread word family including on the Uralic side e.g. Hungarian méz, Finnish and Estonian mesi, met-, Mari мӱ /my/, Komi ма /ma/ 'honey', suggesting Proto-Uralic ; and on the Indo-European side, English mead, Greek methu 'wine', German Met 'honey wine', Slavic medъ and Sanskrit mádhu 'honey' etc.
There are several criteria to date such borrowings, the most reliable ones coming from historical phonology. For example, Finnic porsas, Erzya пурцос /purt͡sos/, Mokša пурьхц /pur̥ʲt͡s/ 'piglet' presuppose a common proto-form *porćas at an earlier stage of development. This is etymologized as a loanword from PIE *porḱ-, which gives Latin porcus 'hog', Slavic porsę 'pig', OE fearh, Lithuanian par̃šas 'piglet, castrated boar'. Here loaning must have occurred predating the depalatalization of centum languages, and the later development into the Baltic *š reflected as Finn. h in borrowings, or Iranian *c medially reflected as Finn. t. If the PIE distinction between palatovelars and plain velars is reconstructed as one of velars and uvulars, then instead of the former condition also a lower limit can be set up for the loan, as postdating the satemization of *ḱ into a palatalized stop or affricate.
Work particularly associated with research of the scholar Jorma Koivulehto has identified several additions to the list of Finnic loanwords from an Indo-European source or sources whose particular interest is the apparent correlation of PIE laryngeals with three post-alveolar phonemes in the Finnic forms. If so, this would point to great antiquity for the borrowings, since no attested Indo-European language neighbouring Uralic has consonants as reflexes of laryngeals. And it would bolster the idea that laryngeals were phonetically distinctly consonantal.
However, Koivulehto's theories are not universally accepted and have been sharply criticized because many of the reconstructions involve a great deal of far-fetched hypotheses and the chronology is not in good agreement with the history of Bronze Age and Iron Age migrations in the Eastern Europe established by archaeologists and historians.
Three Uralic phonemes have been posited to reflect PIE laryngeals. In post-vocalic positions both the post-alveolar fricatives that ever existed in Uralic are represented: firstly a possibly velar one, theoretically reconstructed much as the PIE laryngeals, in the very oldest borrowings and secondly a grooved one in some younger ones. The velar plosive k is the third reflex and the only one found word-initially. In intervocalic position, the reflex k is probably younger than either of the two former ones. The fact that Finno-Ugric may have plosive reflexes for PIE laryngeals is to be expected under well documented Finnic phonological behaviour and does not mean much for tracing the phonetic value of PIE laryngeals, Finnish kärsiä 'suffer, endure' < PGmc *xarđia- 'endure', Finnish pyrkiä < PGmc. *wurk.
The correspondences do not differentiate between, and. Thus
  1. PIE laryngeals correspond to the PU laryngeal *x in wordstems like:
  2. *Finnish na-inen 'woman' / naa-ras 'female' < PU *näxi-/*naxi- < PIE * = */-/ > Sanskrit gnā́ 'goddess', OIr. mná, ~ Greek gunē 'woman'
  3. *Finnish sou-ta- ~ Samic *sukë- 'to row' < PU *suxi- < PIE *sewh-
  4. *Finnish tuo- 'bring' ~ Samic *tuokë- ~ Tundra Nenets tāś 'give' < PU *toxi- < PIE * = *// > Greek didōmi, Lat. dō-, Old Lith. dúomi 'give', Hittite dā 'take'
  5. :Note the consonantal reflex /k/ in Samic.
  6. PIE laryngeals correspond to Finnic *h, whose normal origin is a Pre-Finnic fricative *š in wordstems like:
  7. *Finnish rohto 'medical plant, green herb' < PreFi *rošto < PreG *groH-tu- > Gmc. *grōþu 'green growth' > Swedish grodd 'germ '
  8. *Old Finnish inhi- 'human being' < PreFi *inši- 'descendant' < PIE *e/o- > Sanskrit jā́- 'born, offspring, descendant', Gmc. *kunja- 'generation, lineage, kin'
  9. PIE laryngeals correspond to Pre-Finnic *k in wordstems like:
  10. *Finnish kesä 'summer' < PFS *kesä < PIE * > Balto-Slavic *eseni- 'autumn', Gothic asans 'summer'
  11. *Finnish kaski 'burnt-over clearing' < Proto-Finnic *kaski < PIE/PreG * = *// > Gmc. *askōn 'ashes'
  12. *Finnish koke- 'to perceive, sense' < PreFi *koki- < PIE * = *// > Greek opsomai 'look, observe'
  13. *Finnish kulke- 'to go, walk, wander' ~ Hungarian halad- 'to go, walk, proceed' < PFU *kulki- < PIE *kʷelH-e/o- > Greek pelomai ' to be moving', Sanskrit cárati 'goes, walks, wanders ', cognate Lat. colere 'to till, cultivate, inhabit'
  14. *Finnish teke- 'do, make' ~ Hungarian tëv-, të-, tesz- 'to do, make, put, place' < PFU *teki- < PIE > Greek títhēmi, Sanskrit dádhāti 'put, place', but 'do, make' in the western IE languages, e.g. the Germanic forms do, German tun, etc., and Latin faciō.
This list is not exhaustive, especially when one also considers several etymologies with laryngeal reflexes in Finno-Ugric languages other than Finnish. For most cases no other plausible etymology exists. While some single etymologies may be challenged, the case for this oldest stratum itself seems conclusive from the Uralic point of view, and corresponds well with all that is known about the dating of the other most ancient borrowings and contacts with Indo-European populations. Yet acceptance for this evidence is far from unanimous among Indo-European linguists, some even regard the hypothesis as controversial.

PIE Laryngeals and Proto-Semitic

Several linguists have posited a relationship between PIE and Semitic, almost right after the discovery of Hittite. Among these were Hermann Möller, though a few had argued that such a relationship existed long before the 20th century, like Richard Lepsius in 1836. The postulated correspondences between the IE laryngeals and that of Semitic assist in demonstrating their evident existence. Given here are a few lexical comparisons between the two respective proto-languages based on Blažek, who discusses these correspondences in the context of a proposed relation between IE and Afroasiatic, the language family to which the Semitic languages belong:
  1. Semitic ʼ-b-y 'to want, desire' ~ PIE * 'to fuck'
  2. Semitic ʼ-m-m/y ~ PIE * 'to take'
  3. Semitic ʼin-a 'in', 'on', 'by' ~ PIE * > Sanskrit ni, ~ Greek enōpḗ
  4. Semitic ʼanāku ~ PIE *h₁eǵ- 'I'
  5. Semitic ʻ-d-w 'to pass, move, run' ~ PIE * 'to pass through'
  6. Semitic ʻ-l-y 'to rise, grow, go up, be high' ~ PIE * 'to grow, nourish'
  7. Semitic ʻ-k-w: Arabic ʻakā 'to rise, be big' ~ PIE * 'to grow, nourish'
  8. Semitic ʻl 'next, in addition' ~ PIE * 'in'
  9. Semitic: Arabic ʻanan 'side', ʻan 'from, for; upon; in' ~ PIE * 'on'

    Explanation of ablaut and other vowel changes

A feature of Proto-Indo-European morpheme structure was a system of vowel alternations termed ablaut by early German scholars and still generally known by that term. Several different such patterns have been discerned, but the commonest one, by a wide margin, is e/o/∅ alternation found in a majority of roots, in many verb and noun stems, and even in some affixes. The different states are called ablaut grades; e-grade and o-grade are together "full grades", and the total absence of any vowel is "zero grade".

Examples

Root *''sed''

Thus the root *sed- "to sit " has three different shapes: *sed-, *sod-, and *sd-. This kind of patterning is found throughout the PIE root inventory and is transparent:
In addition to the commonplace roots of consonant + vowel + consonant structure, there are also well-attested roots like *dhē- "put, place" and *dō- "give" : these end in a vowel, which is always long in the categories where roots like *sed- have full grades; and in those forms where zero grade would be expected, if before an affix beginning with a consonant, we find a short vowel, reconstructed as *ə, or schwa. An "independent schwa", like the one in PIE *pǝter- "father", can be identified by the distinctive cross-language correspondences of this vowel that are different from the other five short vowels.
Whatever caused a short vowel to disappear entirely in roots like *sed-/*sod-/*sd-, it was a reasonable inference that a long vowel under the same conditions would not quite disappear, but would leave a sort of residue. This residue is reflected as i in Indic while dropping in Iranian; it gives variously e, a, o in Greek; it mostly falls together with the reflexes of PIE *a in the other languages :
Conventional wisdom lined up roots of the *sed- and *dō- types as follows:
Full GradesWeak GradesMeaning
sed-, sod-sd-"sit"
dō-də-"give"
stā-stə-"stand"

But there are other patterns of "normal" roots, such as those ending with one of the six resonants, a class of sounds whose peculiarity in Proto-Indo-European is that they are both syllabic and consonants, depending on what sounds are adjacent:

Root *''bher-/bhor-/bhṛ- ~ bhr''

Saussure's insight was to align the long-vowel roots like *dō-, *stā- with roots like *bher-, rather than with roots of the *sed- sort. That is, treating "schwa" not as a residue of a long vowel but, like the *r of *bher-/*bhor-/*bhṛ-, an element that was present in the root in all grades, but which in full grade forms coalesced with an ordinary e/o root vowel to make a long vowel, with "colouring" of the e-grade into the bargain; the mystery element was seen by itself only in zero grade forms:
Full GradesZero GradeMeaning
bher-, bhor- / bhr-"carry"
deX, doX- / dX-"give"

Saussure treated only two of these elements, corresponding to our *h₂ and *h₃. Later it was noticed that the explanatory power of the theory, as well as its elegance, were enhanced if a third element were added, our *h₁, which has the same lengthening and syllabifying properties as the other two but has no effect on the colour of adjacent vowels. Saussure did not suggest as to the phonetics of these elements; his term for them, "coefficients sonantiques", was not however a fudge, but merely the term in general use for glides, nasals, and liquids as in roots like *bher-.
As mentioned above, in forms like *dwi-bhr-o-, the new "coefficients sonantiques" have no reflexes at all in any daughter language. Thus the compound *'- "to 'fix thought', be devout, become rapt" forms a noun *- seen in Proto-Indo-Iranian *mazdha- whence Sanskrit medhá- /mēdha/ "sacrificial rite, holiness", Avestan mazda- "name of the greatest deity".

Root ''*bhendh''

There is another kind of unproblematic root, in which obstruents flank a resonant. In the zero grade, unlike the case with roots of the *bher- type, the resonant is therefore always syllabic. An example would be *bhendh- "tie, bind":
This is all straightforward and such roots fit directly into the overall patterns. Less so are certain roots that seem sometimes to go like the *bher- type, and sometimes to be unlike anything else, with long syllabics in the zero grades while at times pointing to a two-vowel root structure. These roots are variously called "heavy bases", "disyllabic roots", and "seṭ roots".

Root ''*ǵen'', ''*ǵon'', ''*ǵṇn-/*ǵṇ̄''

For example, the root "be born, arise" is given in the usual etymological dictionaries as follows:
The forms occur when the root is followed by an affix beginning with a vowel; the forms when the affix begins with a consonant. As mentioned, the full-grade forms look just like the *bher- type, but the zero grades always and only have reflexes of syllabic resonants, just like the *bhendh- type; and unlike any other type, there is a second root vowel following the second consonant:
;*ǵen-
;*ǵon-
;*ǵṇn-/*ǵṇ̄-
On the term "seṭ". The Pāṇinian term "seṭ" is literally "with an /i/". This refers to the fact that roots so designated, like jan- "be born", have an /i/ between the root and the suffix, as we've seen in Sanskrit jánitar-, jániman-, janitva. Cf. such formations built to "aniṭ" roots, such as han- "slay": hántar- "slayer", hanman- "a slaying", hantva. In Pāṇini's analysis, this /i/ is a linking vowel, not properly a part of either the root or the suffix. It is simply that some roots are in effect in the list consisting of the roots that "take an -i-".
But historians have the advantage here: the peculiarities of alternation, the "presence of /i/", and the fact that the only vowel allowed in second place in a root happens to be *ə, are all neatly explained once *ǵenə- and the like were understood to be properly *ǵenH-. That is, the patterns of alternation, from of Indo-European, were simply those of *bhendh-, with the additional detail that *H, unlike obstruents would become a syllable between two consonants, hence the *ǵenə- shape in the Type formations, above.

Discussion

The startling reflexes of these roots in zero-grade before a consonant is explained by the lengthening of the syllabic resonant before the lost laryngeal, while the same laryngeal protects the syllabic status of the preceding resonant even before an affix beginning with a vowel: the archaic Vedic form jajanur cited above is structurally quite the same as a form like *' "they saw" < *'.
Incidentally, redesigning the root as *ǵenH- has another consequence. Several of the Sanskrit forms cited above come from what look like o-grade root vowels in open syllables, but fail to lengthen to -ā- per Brugmann's law. All becomes clear when it is understood that in such forms as *ǵonH- before a vowel, the *o is not in fact in an open syllable. And in turn, that means that a form like jajāna "was born", which apparently does show the action of Brugmann's law, is a false witness: in the Sanskrit perfect tense, the whole class of seṭ roots, en masse, acquired the shape of the aniṭ 3sing. forms.

Other roots

There are also roots ending in a stop followed by a laryngeal, as *'- "spread, flatten", from which Sanskrit '- "broad" masc., pṛthivī- fem., Greek platús ; Skt. prathimán- "wideness", Greek platamṓn "flat stone". The laryngeal explains the change of *t to *th in Proto-Indo-Iranian, the correspondence between Greek -a-, Sanskrit -i- and no vowel in Avestan.
Stray laryngeals can be found in isolated or seemingly isolated forms; here the three-way Greek reflexes of syllabic *h₁, *h₂, *h₃ are particularly helpful, as seen below.
The Greek forms ánemos and árotron are particularly valuable because the verb roots in question are extinct in Greek as verbs. This means that there is no possibility of some sort of analogical interference, for example, happened in the case of Latin arātrum "plow", whose shape has been distorted by the verb arāre "to plow". It used to be standard to explain the root vowels of Greek thetós, statós, dotós "put, stood, given" as analogical. Most scholars nowadays probably take them as original, but in the case of "wind" and "plow", the argument can't even come up.clarification and citation needed: consider "νέμω", seeing as "άνεμος" can be defined as that which is without "νομή"
Regarding Greek híeros, the pseudo-participle affix *-ro- is added directly to the verb root, so *'- > *isero- > *ihero- > híeros, and Sanskrit iṣirá-. There seems to be no question of the existence of a root *eysH- "vigorously move/cause to move". If the thing began with a laryngeal, and most scholars would agree that it did, it would have to be *h₁-, specifically; and that's a problem. A root of the shape *h₁eysh₁- is not possible. Indo-European had no roots of the type *mem-, *tet-, *dhredh-, i.e., with two copies of the same consonant. But Greek attests an earlier form of the same meaning, híaros. If we reconstruct *h₁eysh₂-, all of our problems are solved in one stroke. The explanation for the híeros/híaros business has long been discussed, without much result; laryngeal theory now provides the opportunity for an explanation which did not exist before, namely the metathesis of the two laryngeals. It is still only a guess, but it is a much simpler and more elegant guess than the guesses available before.
The syllabic *' in *- "father" might not be isolated. Certain evidence shows that the kinship affix seen in "mother, father" etc. might have been *-h₂ter- instead of *-ter-. The laryngeal syllabified after a consonant but lengthened a preceding vowel.

Laryngeals in morphology

Like any other consonant, Laryngeals feature in the endings of verbs and nouns and derivational morphology, the only difference being the greater difficulty of telling what's going on. Indo-Iranian, for example, can retain forms that pretty clearly reflect a laryngeal, but there is no way of knowing which one.
The following is a rundown of laryngeals in Proto-Indo-European morphology.
Throughout its history, the laryngeal theory in its various forms has been subject to extensive criticism and revision.
The original argument of Saussure was not accepted by anyone in the Neogrammarian school, primarily based at the University of Leipzig, then reigning at the cutting-edge of Indo-European linguistics. Several of them attacked the Mémoire savagely. Osthoff's criticism was particularly virulent, often descending into personal invective.
For the first half-century of its existence, the laryngeal theory was widely seen as ‘an eccentric fancy of outsiders’. In Germany it was roundly rejected. Among its early proponents were Hermann Möller, who extended Saussure's system with a third, non-colouring laryngeal, Albert Cuny, Holger Pedersen, and :sl:Karel Oštir|Karl Oštir. The fact that these scholars were engaged in highly speculative long-range linguistic comparison further contributed to its isolation.
Although the founding fathers were able to provide some indirect evidence of a lost consonantal element, the direct evidence so crucial for the Neogrammarian thinking was lacking. Saussure's structural considerations were foreign to the leading contemporary linguists.
After Kuryłowicz's convincing demonstration that the Hittite language preserved at least some of Saussure's coefficients sonantiques, the focus of the debate shifted. It was still unclear how many laryngeals are to be posited to account for the new facts and what effect they have had exactly. Kuryłowicz, after a while, settled on four laryngeals, an approach further accepted by Sapir, Sturtevant, and through them much of American linguistics. The three-laryngeal system was defended, among others, by Walter Couvreur and Émile Benveniste. Many individual proposals were made, which assumed up to ten laryngeals. While some scholars, like :de:Heinz Kronasser|Heinz Kronasser and Giuliano Bonfante, attempted to disregard Anatolian evidence altogether, the ‘minimal’ serious proposal was put forward by Hans Hendriksen, :sv:Louis Hammerich|Louis Hammerich and later Ladislav Zgusta, who assumed a single /H/ phoneme without vowel-colouring effects.
By the 2000s, however, a widespread, though not unanimous, agreement was reached in the field on reconstructing Möller's three laryngeals. One of the last major critics of this approach was Oswald Szemerényi, who subscribed to a theory similar to Zgusta's.
Today the laryngeal theory is almost universally accepted in this new standard form. Nevertheless, marginal attempts to undermine its bases are occasionally undertaken.