Proto-West Persian'

The branch further divides into the Bustaxoid and Tsonboid languages.

Changes from Proto-Persian':

• high vowels
  • ɪ ʊ ɪː ʊː → i u əj əw
  • ɪw ɪj ʊj → iw iː uj
• loss of difthongs in _w
  • k → kʷ / w_C
  • iw → yː
  • ew → e₂ː
  • æw → æː
  • ow → uː
  • əw → o₁ː
• stop phonation/MOA changes
  • intervocalic lenition
    • b d → β ð
  • intervocalic voicing
    • p t k q → b d g ɢ
  • loss of aspiration
    • ʰp ʰt ʰk(ʷ) ʰq → p t k(ʷ) q
    • pʰ tʰ kʰ qʰ → ɸ θ x χ
  • stop clusters with a 2nd voiced member become voiced thruout
• lo vowels
  • æ ɐ æː ɒː → a ə aː o₂ː

Two distinct types of /eː oː/ are reconstructed for PWP'. Most likely these are /eː oː/ and /ɛː ɔː/, but it remains unclear which are which. An alternate theory proposes /øː ɤː/ insted but with little additional clarification.

No evidence exists of labialized uvulars.