ABSTRACT
Nearly all scholars agree that Proto-Basque had a simple five-vowel system with vowels *i *e *u *o *a and no vowel length. This chapter reviews the foundations of that position and presents a re-evaluation of Michelena’s proposed falling diphthongs. In nearly all cases, these diphthongs are suspect. Three unique contributions to the study of Proto-Basque vowels are offered. First, there is recognition of a special class of disyllabic *h-medial roots. One special property of these roots is that they cannot begin with voiceless stops. A second feature of the Proto-Basque vowel system that is formalized is prosodically conditioned vowel neutralization and loss in historical compounding. A third finding is that, though, overall, vowels have been relatively stable in the history of the language, the methods of internal reconstruction used in this volume reveal a large number of root-sets of two, three, and four members, where roots have similar meanings but distinct vocalism. Some of these root-sets play an important role in the external comparison with Proto-Indo-European offered in Part II.
