Major Sanjeev are those languages that from the very beginning of its history were in close contact with each other and had a common literary culture, shaped more or less uniform group and currently have the status of official languages. This is a Mongolian, Buryat and Kalmyk. Marginalized or "island" language of the author considers all the other languages that have no written language and are separated from the main habitat of the Mongolian other language groups: Chinese, Iranian and Tibetan. In the classification of ta Bertagaeva languages are divided into phonetic features. Since the author shares the Mongolian languages into three groups: anlautno-vocal-anlautno spirantnye and mixed languages. The first group coincides with the main group on the classification , the second group includes all other languages, except the Mongolian language, and the third group – is actually the Mongolian language, as well as a written language drevnemongolsky and so-called "Square script".
In XVI-XVII centuries, a single Mongolian language was divided into dialects, which in varying degrees different from each other (in phonetics, vocabulary). And the Mongolian language is more closely related languages than the language family. Particular similarities are the main languages of the group (). A marginal languages quite different from each other, since their formation have had some influence other language groups are located (geographically) close to them. However, for the determination of the Mongolian languages often still use the term Mongolian language family, part of the Altaic language phylum. Mongolians have been established on Throughout their history, many different writing systems.