The monograph is the sixth, final, book of collective work "Comparative historical grammar of Turkic languages." It contains an essay on the reconstructed phonetics and morphology of the Praturk language state, as well as a number of lexical areas important in ethnocultural terms, and an attempt was made to reduce the dating of the collapse of the Turkic family of languages ​ ​ into separate language subgroups obtained by various methods, in particular by analyzing contact phenomena.