The inhabitants of Rwanda and Burundi belong to several different ethnic groups: Hutu (84%), Tutsi, including Hima (15%), and Twa (1%) (a pygmy people). The fact that these ethnic groups share the same language is assumed to be the result of the Hutu outnumbering the latter two groups (see Hutu for a more complete historical perspective).
Neighboring dialects of Rundi are mutually intelligible with Ha, a language spoken in western Tanzania.