Uzbek is a Karluk Turkic language spoken by Uzbeks. It is the official and national language of Uzbekistan and formally succeeded Chagatai, an earlier Karluk language endonymically called Türki or Türkçe, as the literary language of Uzbekistan in the 1920s. According to the Ethnologue, Southern Uzbek and Standard Uzbek are spoken as a native language by more than 34 million people around the world, making Uzbek the second-most widely spoken Turkic language after Turkish. In addition to these native speakers, there are members of many other ethnic groups such as Tajiks, Kazakhs, and Russians who live in Uzbekistan and speak Uzbek as their second language. There are two major variants of the Uzbek language: Northern Uzbek, or simply "Uzbek", spoken in Uzbekistan, Kyrgyzstan, Kazakhstan, Tajikistan, Turkmenistan and China; and Southern Uzbek, spoken in Afghanistan and Pakistan. Both Northern and Southern Uzbek are divided into many dialects. Uzbek and Uyghur are sister languages and they constitute the Karluk or "Southeastern" branch of Turkic. External influences on Uzbek include Arabic, Persian, and Russian. One of the most noticeable distinctions of Uzbek from other Turkic languages is the rounding of the vowel /ɑ/ to /ɒ/ under the influence of Persian. Unlike other Turkic languages, vowel harmony is almost completely lost in modern Standard Uzbek, though it is still observed to some degree in its dialects, as well as in Uyghur. Different dialects of Uzbek show varying degrees of influence from other languages such as Kipchak and Oghuz Turkic (for example, in grammar) as well as Persian (in phonology), which gives literary Uzbek the impression of being a mixed language. In February 2021, the Uzbek government announced that Uzbekistan plans to fully transition the Uzbek language from the Cyrillic script to a Latin-based alphabet by 1 January 2023. Similar deadlines had been extended several times. As of 2024, most institutions still use both alphabets.