The article includes vowel harmony, which is considered one of the most characteristic features of the Turkic languages. Vowel harmony has a very ancient history in Turkic. This law was formed during the period of the proto-Turkic. In the ancient Turkic written monuments, vowel harmony was an “iron law”. This law has played a key role in the writing of ancient written monuments. However, although vowel harmony came from Orkhon, this ancient phonetic law should always be considered a continuation of the old norm. Although the word “vowel harmony” as a phonetic law in Turkic includes harmony of consonants, the harmony of vowels with consonants, on the basis of this law stands harmony of the vowel. However, as a result of the internal and exte...