PIE thematic vowel

The thematic vowel was an ablauting suffix -e/o- that could occur at the end of stems. It was largely functionless but was part of a large number of suffixes for both PIE verb stem formation and PIE nominal stem formation. Perhaps the only time it was meaningful on its own was in the formation of the Core IE thematic subjunctive.

Thematic vowels followed a special version of the usual ablaut rules, namely:¹

∅-grade only occurs when followed by particular derivational suffixes (such as -yó-)
For verbs, e-grade only occurred:
- word-finally, i.e. active 2sg. imperative, e.g. wérye ‘say!’
- in e-grade Core IE double thematic subjunctive
- before coronal obstruents. e.g. imperative 2sg. wéryeti ‘you say’
For nominals, the e-grade only occurred
- word finally, e.g. voc sg. swéḱure ‘father-in-law!’
- before h₂ as a (by PIE *e-laryngeal colouring), e.g. neut. collective werǵáh₂ ‘work’

Since o occurred in all other cases, thematic stems are sometimes called o-stems.

jaj•a•person's notes