Segments
All Basque dialects have five oral vowel phonemes, /i/, /e/, /a/, /o/, /u/, which make up a system with three degrees of openness and three orders of localisation, as shown below:
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Front |
Central |
Back |
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Close |
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Half-close |
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Open |
The back series is labialised and the front series is non-labialised. The Souletine dialect – and some neighbouring subdialects of the Eastern Lower Navarrese dialect- also have a sixth vowel [y], a back, close and labialised vowel, usually written as <ü>, whose phonemic character is argued.
In addition, the Souletine dialect has nasal vowels, which were also present in the other dialects but gradually disappeared over different periods of time.At present, the phonemic character of specific vowels of Souletine, [ĩ], [ỹ], [ẽ], [ã], [ũ], is questionable and should be reviewed.
Overall, there has traditionally been a great instability in the vowel pitch, which has led to the appearance of frequent changes (assimilation, dissimilation, metathesis, etc.), favoured by certain phonic positions and contexts, which generally have a diatopic distribution.
