Lakota is a Siouan language

Siouan languages

The Western Siouan languages, also called Siouan proper or simply Siouan, are a Native American language family of North America, and the second largest indigenous language family in North America, after Algonquian...

 spoken by the Lakota people of the Sioux

Sioux

The Sioux are Native American and First Nations people in North America. The term can refer to any ethnic group within the Great Sioux Nation or any of the nation's many language dialects...

 tribes. While generally taught and considered by speakers as a separate language, Lakota is mutually understandable with the other two languages (cf. Dakota language

Dakota language

Dakota is a Siouan language spoken by the Dakota people of the Sioux tribes. Dakota is closely related to and mutually intelligible with the Lakota language.-Dialects:...

), and is considered by most linguists one of the three major varieties

Variety (linguistics)

In sociolinguistics a variety, also called a lect, is a specific form of a language or language cluster. This may include languages, dialects, accents, registers, styles or other sociolinguistic variation, as well as the standard variety itself...

 of the Sioux language

Sioux language

Sioux is a Siouan language spoken by over 33,000 Sioux in the United States and Canada, making it the fifth most spoken indigenous language in the United States or Canada, behind Navajo, Cree, Inuit and Ojibwe.-Regional variation:...

. The Lakota language represents one of the largest Native American language speech communities in the United States, with approximately 6,000 speakers living mostly in northern plains states of North Dakota

North Dakota

North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....

 and South Dakota

South Dakota

South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

.

The language was first put into written form by missionaries around 1840 and has since evolved to reflect contemporary needs and usage.
Lakota has five oral vowels, /i e a o u/, and three nasal vowels, /ĩ ã ũ/ (phonetically [ɪ̃ ə̃ ʊ̃]).