Quantitative metathesis


Quantitative metathesis is a specific form of metathesis or transposition involving quantity or vowel length. By this process, two vowels near each other – one long, one short – switch their lengths, so that the long one becomes short, and the short one becomes long.
In theory, the definition includes both
and
but Ancient Greek, which the term was originally created to describe, displays only the former, since the process is part of long-vowel shortening.

Ancient Greek

In the Attic and Ionic dialects of Ancient Greek, ēo and ēa often exchange length, becoming eō and eā.
This quantitative metathesis is more accurately described as one form of long-vowel shortening. Usually if quantitative metathesis affects a word, other kinds of shortening do as well, in the forms where quantitative metathesis cannot occur:
In general, the vowels affected by this shortening were separated by the Proto-Indo-European semivocalic versions of u or i, usually deleted in later Greek: w or y.

First declension

The Homeric form of the genitive singular in the masculine first declension sometimes undergoes quantitative metathesis:
The Attic genitive singular Πηλεΐδ-ου Pēleḯd-ou uses a copy of the second-declension ending, which came from the same original form as the Thessalian Aeolic ending -oio. The Homeric form comes from the same case ending, with the first-declension pseudo-thematic vowel ā.

Second declension

Nouns in a small subclass of the second declension lengthen the o, oi of the ending to ō, ōi. Sometimes this is quantitative metathesis:
But sometimes, when a long vowel occurs in the ending, ē is shortened to e without an accompanying lengthening of the vowel in the ending :

Third declension

Some third-declension nouns had, in Proto-Indo-European, stems in -u or -i in zero-grade, -ew or -ey in short e-grade, and -ēw or -ēy in long ē-grade. Others had -āw with no variation in ablaut grade, which changed in some forms to ēw, by the Attic-Ionic ā → ē shift.
In many cases, the w or j was deleted, but sometimes it is preserved as the last element of a diphthong.
Stems with ē underwent shortening in Classical Attic-Ionic, but early forms with long ē are preserved in Homer to maintain the original meter. Some forms exemplify the quantitative-metathesis type of shortening:
The accent of the genitive singular of the last two words violates the rules of accentuation. Normally the long vowel of the last syllable would force the accent forward to the second-to-last syllable, giving *πολέως *poléōs and *ἀστέως *astéōs, but instead the accent remains where it was before shortening.
Other forms of these nouns shorten ē to e, but because the vowel of the ending is long, no quantitative metathesis occurs:
Some forms shorten ē to e before i according to the analogue of the other forms, but without lengthening the i:
Other forms involve no shortening, since they come from a short e-grade form of the stem. The accent of the genitive plural is sometimes irregular because it follows the analogue of the genitive singular:
The perfect participle of the verb θνῄσκω thnēískō "die" undergoes vowel shortening, and quantitative metathesis in the oblique forms: