In the traditional formulation there are three laryngeals: h1, h2, h3. The laryngeals h2 and h3 had the property of "colouring" an adjacent e, i.e. to change it respectively to a and to o. At a later stage, the laryngeals went lost in most positions, sometimes with a phonological consequence and sometimes leaving no trace at all, depending on the context and the language.
- PIE dheh1 in Greek τίθημι (I set), Latin fēcī (I did), Gotic gadēds (deed);
- PIE steh2 in Doric Greek ἵστᾱμι (I put), Latin stāmen (warp = standing thread in a vertical loom);
When a laryngeal lay between consonants, a short vowel is found at its place. In Greek, h1 > e, h2 > a, and h3 > o. In Indo-Iranian languages such as Sanskrit, each laryngeal becomes i, and in all other Indo-European languages, each laryngeal becomes a. This explains such observed phenomena as:
- PIE *ph2tér; Greek πατηρ; Sanskrit pitá; Latin pater (father)
- PIE *ish1ros; Greek 'ιερος, Sanskrit is.irá- (sacred)
- PIE *dh3tos; Greek δοτος, Latin datus (given)
The elaboration of this theory is largely due to Ferdinand de Saussure who first proposed it in 1879. However he did not call them laryngeals but coefficients, because there was no clue to how they were actually pronounced. He wrote them E, A, O; In fact they were most often considered vowels. Another widely used notation was ə1, ə3, ə3.
The laryngeals were three consonant sounds that appear in most current reconstructions of the Proto-Indo-European language. The theory was first proposed by Ferdinand de Saussure in 1879; however, it did not begin to achieve any general acceptance until Hittite was discovered and slowly deciphered in the mid-20th century. It soon became apparent that Hittite had phonemes for which the laryngeal theory was the best explanation, and as such the laryngeal theory is accepted by most Indo-Europeanists.
The existence of these sounds was not suspected for quite some time, because Hittite and the Anatolian languages are the only Indo-European languages in which they ever survive as actual phonemes that appear in the records we have of those extinct languages. That said, the existence of these sounds is now accepted by most philologists, because positing their existence simplifies some otherwise hard to explain sound changes that appear in the descendant languages of PIE.
The chief evidence of laryngeals was the fact that when they appeared in connection with the PIE vowel *e-, h2 coloured it to *a-, and h3 to *o-. In Anatolian, however, h2 was preserved, and h3 was preserved in certain positions. For example:
- PIE: *h2enti; Hittite hanti; Latin ante (before, against)
- PIE: *h3eui-; Luwian hawi-; Latin ovis (sheep)
The laryngeal theory has been posited as the best explanation of the otherwise mysterious appearance of h- in the Anatolian words, and the vowel difference between the Anatolian languages and most other Indo-European languages, such as Latin ovis.
The laryngeal theory requires fairly widespread adjustments in our view of the inflections of Indo-European. We now know that PIE may have had two original grammatical genders, masculine and neuter. The feminine gender that most of the oldest Indo-European languages share may have been formed by a suffix, *-eh2, which was coloured by the laryngeal to *-a. This makes the feminine nouns and adjectives originally consonant stems rather than original vowel stems, and helps explain why they are inflected differently from other nouns that are true vowel stems.
The laryngeal theory also explains a number of different ablaut sequences that appear in many Indo-European roots, and makes them seem less arbitrary and more regular. For example, the observed sequences:
- ê/ô/ə is explained as eh1/oh1/h1;
- â/ô/ə is explained as eh2/oh2/h2;
- ô/ô/ə is explained as eh3/oh3/h3
Considerable debate still surrounds the pronunciation of the laryngeals. Many believe that they represented some sort of glottal stop or pharyngeal; others assume that *h2 was a velar and *h3 was a labiovelar fricative. Further still, others hold that they had no pronunciation at all, and are simply phonetic coefficients.
For further reference:
Robert S. P. Beekes: Comparative Indo-European Linguistics (John Benjamins, 1995) ISBN 1-55619-505-2
Indo-European phonology: http://www.tundria.com/Linguistics/IEPhonol.htm