Stammvokal

Etymology
From.

Noun

 * 1)  thematic vowel, stem vowel characteristic vowel linking a root with its suffixes
 * 2)  root vowel, the (stressed) vowel of the root ≈ stem itself
 * 1)  root vowel, the (stressed) vowel of the root ≈ stem itself
 * 1)  root vowel, the (stressed) vowel of the root ≈ stem itself

Usage notes

 * Sense 2 is unambiguous for languages that have lost thematic vowels, because root and stem thereby become identical. However, such use is also found in reference to languages that retain thematic vowels at least to some degree (like in the quotation above).