This article discusses variant words spoken through front-lingual vowels, with words spoken through back-lingual vowels that have the same meaning. As a result of the development of languages ​​over an infinitely long time, rear-lingual and middle-lingual, both vowels and consonants, moved to the front of the tongue. This, of course, was influenced by natural conditions, changes in the physical data of a person (decrease in growth, decrease in his complexion, etc.). In the article, by means of comparative historical study, the ancient forms of variant words are restored, which in linguistics are called “syngarmonic variants and parelli”.Singharmonic variants are more often found in monosyllables in modern languages, which indicates the historical nature of this phenomenon. The number of synarmonic variants increases sharply if we compare and compare competing roots in a separate language or Turkic languages ​​and their dialects, which are formed as a result of the free exchange of vowels, which do not differ in the lexical and semantic sense. Therefore, in order to prove that the ancient roots of the Kazakh-Turkic words were pronounced with solid vowels, we paid special attention to the correspondence of hard and soft vowels in syngarmonic variants