The Altaic language family is subdivided into the Turkic, Mongolian and the Tungus sub-branches. Some scholars consider Japanese and Korean also to be part of the Altaic family. This link is highly disputable. Some theories link the Altaic languages to the Uralic languages to form an Ural-Altaic language family. However, even the notion of an Altaic language family is still controversial. The similarities in vocabulary and language structure between Turkic, Mongolian and Tungus might as well be the result of language contact. Typological closeness does not inevitably mean genetical relationship. Nevertheless systematic sound correspondences in the genuine vocabulary of the three sub-branches indicate, that Turkic, Mongolian and Tungus are genetically related.
The Altaic language family consists of more than 60 languages with more than 100 million speakers and is geographically distributed roughly from the Balkans in the west to the Okhotsk sea in Eastern Siberia.
Turkic languages are spoken in a vast area that reaches from the Balkans over Turkey, the Caucasus, Iran, Central Asia, northwestern China to northern Siberia. The most prominent representatives of the Turkic languages are Turkic, Azerbaijani, Uzbek, Uyghur, Kazakh and Chuvash. The Turkic languages are also called Chuvash-Turkic languages, because Chuvash differs remarkably from the rest of the Turkic languages. For that reason some scholars consider Chuvash an additional top level constituent of the Altaic language family alongside with Turkic, Mongolian and Tungus.
Speakers of Mongolian languages for the most part live in the Russian Republics of Buryatia and Kalmykia, in the Republic of Mongolia and in Inner Mongolia, which is part of China. The most important members of the Mongolian sub-branch are Mongolian Proper, Buryat and Kalmyk.
Tungus languages are spoken by populations scattered across Siberia and north-western China. The best known language in the Tungus sub-branch is Manchu, which is nearly extinct. Other Tungus languages are Evenki and Even.
Several Altaic peoples have played an important (and belligerent) role in history. The presumably Altaic Huns, who invaded Europe in the 4th and 5th century AD, the Mongols, who established a vast empire in the 13th and 14th century, the Manchu, who ruled China from the 17th to the early 20th century. Two Turkic peoples created empires at the threshold of Europe: the Seljuqs in the 11th and 12th century and the Turks, who founded the Ottoman Empire in the 14th century.
The first written monuments of Altaic languages are the Orkhon inscriptions in the Old Turkic language, which have been found in Mongolia and date back to the 8th century AD.
After World War I many Altaic languages established new writing systems or became written languages for the first time. Turkish, for example, shifted its script from Arabic to Latin. In the Soviet Union Altaic languages first adopted the Latin script, then a Cyrillic based script came in use.
Altaic languages have a rich vocalism, but a relatively small amount of consonants. A major feature in Altaic morphophonology is vowel harmony. Vowel harmony is a set of progressive assimilation rules that affect only vowels. There are two types of vowel harmony that occur in Altaic: palatal and labial vowel harmony. Palatal vowel harmony indicates, that in a given word there can appear either only back vowels or only front vowels. Furthermore front velar consonants /k, g, l/ occur only with front vowels and back velars /q, g., l~/ only with back vowels. In several Altaic languages palatal harmony has been weakened or lost. Turkic and Mongolian also feature labial harmony, Tungus does not. Labial harmony has different shapes in Turkic and Mongolian. In Turkic labial harmony a high vowel gets rounded by a round vowel in the directly preceding syllable, in Mongolian labial harmony a non-high vowel gets rounded by a rounded vowel in the directly preceding syllable.
The morphology of Altaic languages is of the agglutinative type: Morphemes have clear-cut boundaries, grammatical morphemes bear mostly one single meaning, the word stem is not modified by internal inflection like 'umlaut' 'ablaut'. Altaic morphology is almost exclusively suffixing. Nouns and verbs are highly inflected. Altaic noun morphology is rich in cases: Turkish has six, Classical Mongolian has seven cases, and Northern Tungus languages have usually more than ten cases. Adjectives, on the other hand, are not inflected at all and do not agree with their head nouns. An exception to this pattern, however, is found in several Northern Tungus languages, where adjectives are inflected and agree with their head noun in case and number. Altaic languages have no grammatical gender.
There exists a considerably little quantity of common cognate vocabulary among all three sub-branches of Altaic. For example many of the numerals of Turkic, Mongolian and Tungus are not related with each other. Turkic and Mongolian share a bigger amount of cognate vocabulary than these two as a whole share with Tungus. Besides extensive mutual lexical borrowing occurred between Turkic and Mongolian, and Tungus borrowed from the both Turkic and Mongolian.