Consonants

The consonant system had a two-way contrast of stop consonants (fortis vs. lenis), k, p, t vs. g, b, d. There was also an affricate consonant, ç; at least one sibilant s and sonorants m, n, ń, ŋ, r, l with a full series of nasal consonants. Some scholars additionally reconstruct the palatalized sounds ĺ and ŕ for the correspondence sets Oghuric /l/ ~ Common Turkic *š and Oghuric /r/ ~ Common Turkic *z. Most scholars, however, assume that these are the regular reflexes of Proto-Turkic *l and *r.^[9] Oghuric is thus sometimes referred to as Lir-Turkic and Common Turkic as Shaz-Turkic.

A glottochronological reconstruction based on analysis of isoglosses and Sinicisms points to the timing of the r/z split at around 56 BCE–48 CE. As Anna Dybo puts it, that may be associated with

the historical situation that can be seen in the history of the Huns' division onto the Northern and Southern [groups]: the first separation and withdrawal of the Northern Huns to the west has occurred, as was stated above, in 56 BC,... the second split of the (Eastern) Huns into the northern and southern groups happened in 48 AD.^[10]

Dybo suggests that during that period, the Northern branch steadily migrated from Western Mongolia through Southern Xinjiang into the north's Dzungaria and then finally into Kazakhstan's Zhetysu until the 5th century.^[10]

There was no fortis-lenis contrast in word-initial position: the initial stops were always *b, *t, *k, the affricate was always *č (*ç) and the sibilant was always *s. In addition, the nasals and the liquids did not occur in that position either.^[11]

Like in many modern Turkic languages, the velars /k/, /g/, and possibly /ŋ/ seem to have had back and front allophones ([k] and [q], [g] and [ɢ], [ŋ] and [ɴ]) according to their environments, with the velar allophones occurring in words with front vowels, and uvular allophones occurring in words with back vowels. The lenis stops /b/, /d/ and /g/~/ɢ/ may have tended towards fricatives intervocalically.^[12]

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.^[13][14] The phonemicity of the distinction between the two close unrounded vowels, i.e. front *i and back *ï, is also rejected by some.^[14]

Nouns

Plural of nouns are formed by the suffix *-lAr, however, the Chuvash plural -sem <-сем> seems to be a late replacement. Reconstructable possessive suffixes in Proto-Turkic includes 1sg *-m, 2sg *-ŋ, and 3sg *-(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
• 1sg: *-m < *-män < *bän
• 2sg: *-n < *sän
• 3sg: *-∅ < *ï
• 1pl: *-mïz/*-bïz < *bïz
• 2pl: *-sïz < *sïz

Proto-Turkic also involves derivation with grammatical voice suffixes, as in cooperative *körüš, middle *körün, passive *körül, and causative *körtkür.

Pronouns

Numbers