"/a/ has a short mid variant [ʌ] which is morphologically defined." Presumably this means there's a vowel which only occurs in the third-person pronoun prefix? (This wouldn't be unprecedented - there's some language or other, which of course I've completely forgotten, where schwa only occurs in the negation marker, or something like that. Also Spanish /uj/, Chechen /r̥/, Arabic /ɫ/, etc.)