Indo-European Ablaut - Proto-Indo-European

Proto-Indo-European

Proto-Indo-European (PIE) had a regular ablaut sequence that contrasted the five vowel sounds e/ē/o/ō/Ø. This means that in different forms of the same word, or in different but related words, the basic vowel, a short /e/, could be replaced by a long /ē/, a short /o/ or a long /ō/, or it could be omitted (transcribed as Ø).

zero	short	long
Ø	e	ē
	o	ō

When a syllable had a short e, it is said to be in the "e-grade"; when it had no vowel, it is said to be in the "zero grade", etc. Note that when we refer simply to the e-grade or o-grade, the short vowel forms are meant, unless the lengthened grades are specified. The (short) e-grade is sometimes called the full grade.

A classic example of the five grades of ablaut in a single root is provided by the different case forms of two closely related Greek words:

Ablaut grade	PIE (reconstruction)	Greek	(Greek transliterated)	Translation
e-grade or full grade	*ph2-tér-m̥	πα-τέρ-α	pa-tér-a	"father" (noun, accusative)
lengthened e-grade	*ph2-tḗr	πα-τήρ	pa-tḗr	"father" (noun, nominative)
zero-grade	*ph2-tr-és	πα-τρ-ός	pa-tr-ós	"father's" (noun, genitive)
o-grade	*n̥-péh2-tor-m̥	ἀ-πά-τορ-α	a-pá-tor-a	"fatherless" (adjective, accusative)
lengthened o-grade	*n̥-péh2-tōr	ἀ-πά-τωρ	a-pá-tōr	"fatherless" (adjective, nominative)

The syllable in bold is the one being considered. It is crucial also to notice which syllable carries the word stress: the one with the accent mark. In this unusually neat example, a switch to the zero-grade can be seen when the word stress moves to the following syllable, a switch to the o-grade when the word stress moves to the preceding syllable, and a lengthening of the vowel when the syllable is in word-final position. However, as with most PIE reconstructions, scholars differ about the details of this example. It must also be noted that the lengthening of the vowel in the nominative forms listed above is not directly conditioned by ablaut, but is rather a result of Szemerényi's law, in which the older sequences *ph₂-tér-s and *n̥-péh₂-tor-s became *ph₂-tḗr and *n̥-péh₂-tōr. The lengthened grade in these forms is therefore a result of sound change rather than grammar (and the forms themselves were originally in the regular, unlengthened e- and o-grade), although it was later grammaticalised and spread to other words in which the change did not occur.

One way to think of this system is that Proto-Indo-European originally had only one vowel, /e/, and that over time this vowel changed according to phonetic context, so that the language started to develop a more complex vowel-system. Thus it has often been speculated that an original e-grade in pre-Indo-European underwent two changes in some phonetic environments: under certain circumstances it changed its colouring to (long or short) o (the o-grade), and in others it disappeared entirely (the zero-grade). However, this is not certain: the phonetic conditions that controlled ablaut have never been determined, and the position of the word stress may not have been a key factor at all. There are many counterexamples to the proposed rules: thus *deywó- and its nominative plural *-es show pretonic and posttonic e-grade, respectively. (For these reasons, there has been a recent attempt to analyse Early PIE ablaut in terms of introflexion and root-and-pattern-morphology. It has been shown that it seems to be highly likely that Early PIE was of the root-inflexional morphological type, as was Proto-Semitic (see also Proto-Indo-European language).)