Unstressed Mid Vowels in Portuguese

Portuguese has two mid front vowels and two mid front back vowels. They can be high mid or low mid. The quality of the unstressed mid vowels varies from one dialect to another. Let us illustrate with two words.

The word fonologia (phonology) has two mid back vowels. They are in the first two syllables and are unstressed. The stress is penultimate. In northern Brazil the first two mid back vowels are low mid. They can also be called open. However, in southern Brazil, they are high mid or closed. In Portugal, the mid back vowels in the word fonologia are raised and have the quality of [u]. Not all unstressed mid vowels are raised in European Portuguese, but in many cases they are.

Another word with two mid vowels is energia (energy). In this word they are mid front vowels. As in the word fonologia (phonology), the stress is penultimate. In northern Brazil, the mid front vowels are low mid, but in southern Brazil they are high mid. They can also be distinguished with the terms open and closed. However, in Portugal, they are raised and retracted and thus pronounced with a high central unrounded vowel. The high central unrounded vowel does not occur in Brazilian Portuguese. 

The dialects of southern Brazil realize unstressed mid vowels with mid high tongue position, but the dialects of northern Brazil realize them with mid low tongue position. The unstressed mid vowels of northern Brazil can be classified as open, and the unstressed mid vowels of southern Brazil can be classified as closed. European Portuguese is different. The unstressed mid vowels are often raised, but in those cases in which they are not, they are open vowels.