The Eastern Iranian area has been affected by widespread sound changes, e.g. t͡ʃ > ts.
- In Yaghnobi initial *č- was lost, there should be expected from *čatfṓr if Yaghnobi didn't loss the initial syllable due to a stress shift
Lenition of voiced stops
Common to most Eastern Iranian languages is a particularly widespread lenition of the voiced stops *b, *d, *g. Between vowels, these have been lenited also in most Western Iranian languages, but in Eastern Iranian, spirantization also generally occurs in the word-initial position. This phenomenon is however not apparent in Avestan, and remains absent from Ormuri-Parachi.
A series of spirant consonants can be assumed to have been the first stage: *b > *β, *d > *ð, *g > *ɣ. The voiced velar fricative /ɣ/ has mostly been preserved. The labial member has been well-preserved too, but in most languages has shifted from a voiced bilabial fricative /β/ to the voiced labiodental fricative /v/. The dental member has proved the most unstable: while a voiced dental fricative /ð/ is preserved in some Pamir languages, it has in e.g. Pashto and Munji lenited further to /l/. On the other hand, in Yaghnobi and Ossetian, the development appears to have been reversed, leading to the reappearance of a voiced stop /d/. (Both languages have also shifted earlier *θ > /t/.)
The consonant clusters *ft and *xt have also been widely lenited, though again excluding Ormuri-Parachi, and possibly Yaghnobi.
The neighboring Indo-Aryan languages have exerted a pervasive external influence on the closest neighbouring Eastern Iranian, as it is evident in the development in the retroflex consonants (in Pashto, Wakhi, Sanglechi, Khotanese, etc.) and aspirates (in Khotanese, Parachi and Ormuri). A more localized sound change is the backing of the former retroflex fricative ṣ̌ [ʂ], to x̌ [x] or to x [χ], found in the Shughni–Yazgulyam branch and certain dialects of Pashto. E.g. "meat": ɡuṣ̌t in Wakhi and γwaṣ̌a in Southern Pashto, but changes to guxt in Shughni, γwax̌a in Central Pashto and γwaxa in Northern Pashto.