text: Vowels Like most of its descendants, Proto-Turkic exhibited vowel harmony, distinguishing vowel qualities a, ï, o, u vs. ä, e, i, ö, ü, as well as two vowel quantities. Here, macrons represent long vowels. Some scholars (e.g. Gerhard Doerfer) additionally reconstruct a mid back unrounded *ë based on cognate sets with Chuvash, Tuvan and Yakut ï corresponding to a in all other Turkic languages, although these correspondences can also be explained as deriving from *a which underwent subsequent sound changes in those three languages. The phonemicity of the distinction between the two close unrounded vowels, i.e. front *i and back *ï, is also rejected by some.
  Morphology
  Nouns
  Plurals of nouns were formed using the suffix *-An, but it fell into disuse sometime before the split between Common Turkic and Oghuric. Common Turkic languages today use their respective forms of *-lAr, whereas Chuvash uses , which descends from Proto-Turkic *sāyïn ("every"). Reconstructable possessive suffixes in Proto-Turkic includes  *-m,  *-ŋ, and  *-(s)i, plurals of the possessors are formed by *-z in Common Turkic languages.
  Verbs
  The reconstructable suffixes for the verbs include:
  Aorist: *-Vr
  Past: *-dI
  Negative suffix: *-mA
  : *-m < *-män < *bän
  : *-n < *sän
  : *-∅ < *ï
  : *-mïz/*-bïz < *bïz
  : *-sïz < *sïz
  Proto-Turkic also involves derivation with grammatical voice suffixes, as in cooperative *körüš, middle *körün, passive *körül, and causative *körtkür.
  Vocabulary
  Pronouns