The Arapaho language belongs to the Plains Algonquian language family, which is a subset of the greater Algonquian languages, which belong to the parent Algic language family.
Historically, Arapaho is native to the Great Plains, and today it is still spoken in Wyoming and Oklahoma.
There are three Arapaho languages:
Arapaho (Heenetiit) (United States)
Gros Ventre (United States)
Nawathinehena (United States)
Many linguists consider Gros Ventre an Arapaho dialect-- though the two tribes maintain distinct identities, the languages are primarily mutually comprehensible.
Arapaho is closely related to the Blackfoot language and the Cheyenne language.