Various formerly nomadic Native American tribes of the North American Great Plains.
"The Sioux were various formerly nomadic Native American tribes who once roamed the vast grasslands of the North American Great Plains."
In plain English: Sioux is an umbrella term used to describe many different Native American tribes living in North America today.
"The sioux people have lived in this region for thousands of years."
The group of languages spoken by the Sioux.
"The linguist spent years documenting the distinct dialects within the Sioux language family before publishing her findings."
The English word sioux comes from French Sioux, itself derived from an Ojibwe phrase meaning "little snakes." This original name likely referred to the massasauga, a type of small rattlesnake found in their territory.