The Sino-Vietnamese phonetic system was formed in the ninth century. In the heyday of China's ancient society-the Tang Dynasty, the official language at that time also had a far-reaching influence on the language of the surrounding governors. The local upper class in Annan actively studied Chang 'an pronunciation as its pronunciation. By the time of Vietnam's independence in the early 10th century, Vietnamese intellectuals and the upper class were already very familiar with China culture and Chinese characters, and Chinese characters had entered various fields in Vietnam in large numbers.
The evolution from the 36 letters of Middle Ages to the initial consonants of Sino-Vietnamese sounds is regular and systematic. Although voiced initial consonants are incorporated into voiced initial consonants, the difference between voiced initial consonants and voiced initial consonants is often manifested in the difference of tone yin and yang. There is a strong regularity in the evolution from medieval vowels to Sino-Vietnamese vowels. There is a relatively neat correspondence between the eight tones of Chinese and Vietnamese sounds and the four tones and eight tones of Middle Ages.
According to statistics, Chinese loanwords in Vietnamese account for about 60% of the total vocabulary. Sino-Vietnamese Ci is a recording tool of Vietnamese national culture. Vietnamese takes Sino-Vietnamese words and Sino-Vietnamese sounds as a bridge, and absorbs a large number of new words from Chinese to name a series of new concepts and things that were just introduced to Vietnam at that time. Today, Sino-Vietnamese words and their Sino-Vietnamese sounds still have high application value in the social life of ancient Vietnam, the most typical of which is the super ability to create words.