The Turkic languages are spoken in a vast area which reaches from the Balkans, Turkey, the Caucasus, Iran, Central Asia, north-western China to northern Siberia.
The Turkic languages form a top-level constituent of the Altaic language family. Other major branches of the Altaic languages are the Mongolian and the Tungus languages (some scholars consider Japanese and Korean also to be part of the Altaic family). However, the notion of an Altaic language family is still controversial. The similarities between Tungus, Turkic and Mongolian might also be the result of language contact.
The history of the Turkic languages is subdivided into three stages: 1) Ancient Turkic from the 6th century AD to the 10th century AD, 2) Middle Turkic from the 10th century to the 15th century AD, 3) Modern Turkic from the 16th century until today.
The Ancient Turkic period reaches from the first mentioning of Turkic peoples in the 6th century until the 10th century. The first written attestations of Turkic languages date back to the year 691 AD. These are the renowned 'Orkhon Inscriptions', epitaphs written with runic characters. The Uyghur language of the Uyghur empire in Mongolia (744-840) is attested since the mid 8th century AD in runic inscriptions and in manuscripts and inscriptions using the vertical Uyghur script. The Uyghur script has been derived from the Soghdian script. After the Uyghurs were expelled from Mongolia in 840 there were translation of Buddhist texts into Uyghur in northwest China. Some Ancient Turkic texts have also been written with the Indic Brahmi script, the Mainchean script and the Soghdian script, respectively.
The Bolgars are reported since the 6th century AD in southern Russia and in the Volga region. There are no genuine attestations of the Bolgar language. The Bolgar language is only attested by Bolgar loanwords in other languages, for instance Hungarian. The Chuvash language is probably a descendent of the Bolgar language. However, since Chuvas and the remnants of Bolgar are very different from the rest of the Turkic languages, they are not considered part of the Ancient Turkic period.
The Middle Turkic period comprises languages like Karakhanide (11th-13th centuries) and Post-Karakhanide (13th and 14th centuries), which were the literary languages of the Kingdom of the Karakhanides in eastern Turkestan. Khwarezmian Turkish was the literary language of Central Asia since the 13th century. It has been replaced by the closely related Chagatai Turkish as the literary language for that area in the 15th century. Both languages are ancestors of Modern Uzbek. Polovtsian, which is also known as Kuman, was the language of Turkic Nomads in southern Russia including the Crimean peninsula and Central Asia from the 12th to the 16th century. The main record of the Polovtsian language is the renowned 'Codex Cumanicus' from the 14th century. Another representative of Middle Turkic is Old Anatolian, the ancestor of Turkish.
The Modern Turkic languages are subdivided into five major subgroups: 1) Southern Turkic or Oghuz (Turkish, Turkmen, Azerbaijani etc.), 2) Western Turkish or Kipchak (Kazakh, Kirghiz etc.), 3) Eastern Turkic or Chagatay (Uighur, Uzbek etc.), 4) Northern Turkic or Oirot (Yakut etc.) and finally 5) the Bolgar subgroup with Chuvash as the sole member, that is linguistically isolated among the Turkic languages.
Modern Turkic languages are still very similar to each other. The Chuvash language forms a major exception to that pattern. For that reason some scholars consider Chuvash an additional top-level constituent of the Altaic language family alongside with Turkic, Mongolian and Tungus.
Turkic languages are agglutinative languages, i.e. they usually do not modify the stems of words (unlike fusional languages), they use grammatical affixes, which do not merge with each other or with the stem and which mostly bear only one grammatical meaning.
A characteristic of the vowel inventory is the existence of rounded front vowels.
Turkic languages generally feature vowel harmony (as most Altaic languages do). Vowel harmony can be described as a set of regressive assimilation rules that only affect vowels. Turkic vowel harmony can be subclassified into three basic rules: The term 'palatal harmony' denotes a constraint, that appears in most Turkic languages: There can either be only front vowels or back vowels within one word. Consonants in suffixes may sometimes also follow the palatal harmony pattern. 'Labial harmony' means that the epenthetic vowel, that is inserted between a stem ending in a consonant and a suffix with an initial consonant, becomes rounded following a round stem vowel. Labial harmony is also very frequent in the Turkic languages. 'Labial attraction' implies that the next vowel after a rounded vowel has to be rounded, regardless if the vowel is an euphonic epenthetic vowel or a suffix vowel. Labial attraction is found only in a few languages and dialects.
Stress in Turkic languages has phonological status, i.e. it has no fixed position. The stress is mostly dynamic, but there may also occur tonal stress.
The Turkic languages are generally exclusively suffixing languages.
Both noun stem and verb stems can be extended by means of derivation. Derived noun stems as well as denominal verb stems can be derived from noun stems. Derived verb stems as well as denominal noun stems can be derived from noun stems.
Already in the runic inscriptions of the 8th century we find four case distinctions: nominative, accusative, dative, locative. The genitive originally evolved from a denominal adjective with attributive function. In later stages of the Turkic languages additional cases are found: directive, instrumental, ablative, equative etc. The number of case distinctions varies among the individual Turkic languages.
The separation line between nouns and adjectives is blurred. Adjectives can act as nouns and nouns can act as adjectives.
Pronouns are inflected differently from nouns.
The predicate in Turkic languages is intrinsically of nominal or adjectival origin, consisting of a nominal part and an auxiliary verb. However, practically most predicates are not nominal any more in modern Turkic languages. The verb 'to be' does not need to be expressed necessarily, e.g. (Turkish:) bu yer uzak 'This place (is) far'. Verbs agree with the subject.
Converbs are special verb forms, which are neither conjugated nor nominal. In linguistic literature they are sometimes called 'gerunds' or 'verbal adverbs'. They act as adverbs, conjunctions and often they meet the functions of subordinate clauses.
Turkic languages have accusative structure both in morphology and syntax.
In Turkic languages deponents usually precede their head. Adjectives antecede their head nouns. The unmarked word order is SOV. Alternative orders of the constituents are possible under certain contextual conditions, for instance to emphasise a part of speech. Turkic languages normally use postpositions.
Subordinate clauses are atypical in Turkic languages. Instead we find participial and converbial constructions. Relative sentences with the conjunctions kim and ki are a result of Persian influence.