Lakota (also Lakhota, Teton, Teton Sioux) is a Siouan language spoken by the Lakota people of the Sioux tribes. While generally taught and considered by speakers as a separate language, Lakota is mutually understandable with the other two languages, and is considered by most linguists one of the three major varieties of the Sioux language. The Lakota language represents one of the largest Native American language speech communities left in the United States, with approximately 6,000 speakers living mostly in northern plains states of North and South Dakota. The language was first put into written form by missionaries around 1840 and has since evolved to reflect contemporary needs and usage.