Unstressed vowelswere weakened and dropped.
Stressed vowelsunderwent some changes:
· splitting – 1 phoneme split into several allophones which later become separate phonemes
e.g. à a
a à ã
à æ
· merging– separate phonemes become allophones of one phoneme and then disappear and are not distinguished any more as separate phonemes
e.g. a à
ã à a
æ à