The Arapaho Language is the definitive reference grammar of an endangered Algonquian language. Arapaho differs strikingly from other Algonquian languages, making it particularly relevant to the study of historical linguistics and the evolution of grammar.

Andrew Cowell and Alonzo Moss Sr. document Arapaho's interesting features, including a pitch-based accent system with no exact Algonquian parallels, radical innovations in the verb system, and complex contrasts between affirmative and non-affirmative statements.