[4] Characteristic features such as vowel harmony, agglutination, subject-object-verb order, and lack of grammatical gender, are almost universal within the Turkic family.

[7][8] Similarities with the Uralic languages even caused these families to be regarded as one for a long time under the Ural-Altaic hypothesis.

Turkic languages are null-subject languages, have vowel harmony (with the notable exception of Uzbek due to strong Persian-Tajik influence), converbs, extensive agglutination by means of suffixes and postpositions, and lack of grammatical articles, noun classes, and grammatical gender.

[14] Similarly several linguists, including Juha Janhunen, Roger Blench and Matthew Spriggs, suggest that modern-day Mongolia is the homeland of the early Turkic language.

Although the loans were bidirectional, today Turkic loanwords constitute the largest foreign component in Mongolian vocabulary.

Turkic languages also show some Chinese loanwords that point to early contact during the time of Proto-Turkic.

The Compendium of the Turkic Dialects (Divânü Lügati't-Türk), written during the 11th century AD by Kaşgarlı Mahmud of the Kara-Khanid Khanate, constitutes an early linguistic treatment of the family.

[20] The Codex Cumanicus (12th–13th centuries AD) concerning the Northwestern branch is another early linguistic manual, between the Kipchak language and Latin, used by the Catholic missionaries sent to the Western Cumans inhabiting a region corresponding to present-day Hungary and Romania.

Various terminologies from the Turkic languages have passed into Persian, Urdu, Ukrainian, Russian,[23] Chinese, Mongolian, Hungarian and to a lesser extent, Arabic.

[24][verification needed] The geographical distribution of Turkic-speaking peoples across Eurasia since the Ottoman era ranges from the North-East of Siberia to Turkey in the West.

[citation needed] Hruschka, et al. (2014)[30] use computational phylogenetic methods to calculate a tree of Turkic based on phonological sound changes.

In some cases, the form given is found only in some dialects of the language, or a loanword is much more common (e.g. in Turkish, the preferred word for "fire" is the Persian-derived ateş, whereas the native od is dead).

Shared features with languages grouped together as Altaic have been interpreted by most mainstream linguists to be the result of a sprachbund.

[55][56][57] The linguist Kabak (2004) of the University of Würzburg states that Turkic and Korean share similar phonology as well as morphology.