Note 5:

Choice of phonemes and allophones

Sounds written s and z

I consider the sound written s in words like fazes to be an allophone of the phoneme /s/, although in Portugal it nearly always sounds the same or practically the same as phoneme /S/. By considering this [S] as a fully predictable allophone of /s/, and not of /S/, it is easier to explain that:
- Some in Portugal sometimes/almost make it sound [s], not [S].
- Many in Brazil (in São Paulo rather than Rio de Janeiro) use [s] here. See note ²³, item ².
- A written s in this position easily becomes [z] when a word follows that starts with a vowel, whereas a /S/ written ch or x always stays [S].
  (But the problem with this reasoning is that ch and x hardly ever occur in word-final position, so it can't be shown that they behave differently).
On the other hand, one could argue that the written s in casa, which sounds as [z], is also an allophone of /s/, and not of the phoneme /z/. But although the written s predictably changes to [z] when between vowels, it doesn't mean that all sounds [s] change to [z] in that position, which is clear from words like disse and faço. For that reason I chose to count intervocalic [z] written s as part of phoneme /z/.
Likewise, discussion is possible about whether the z in faz belongs to phoneme /Z/, or is a [Z] allophone of phoneme /z/.