
Proto-Indo-European vowels, as the nucleus of a root, might undergo alternation (or ablaut). PIE was hypothesized to have one vowel, /e/, often alternating with [o] or lack of a vowel (a "zero vowel"). Such vowel alternation might vary the grammar, as it still does in English sing, sang, sung (with [in] of sing reflecting older [en]; [an] of sang, older [on]; and [un] of sung, older [n]).
Links in the table below lead to example uses of the [late?] PIE vowel in question.
| Front | Central | Back | ||||
|---|---|---|---|---|---|---|
| Vowel | E | A | O |