A simetria no sistema vocálico do português brasileiro

The phonological system of Brazilian Portuguese has two rules of neutralization in favor of high vowels and not three, as it has been postulated. The asymmetrical subsystem of four pos- tonic vowels in non-final position is only an effect of frequency, for both middle vowels /e, o/ are shown to be sensitive to raising. It seems to be a case of expansion of the minimum system of three vowels which, in search of regularization, causes variation between two subsystems, the one with five and the one with three vowels