The seven Southern Athabaskan languages can be divided into 2 groups according to the classification of Harry Hoijer: (I) Plains and (II) Southwestern.
Plains Apache is the only member of the Plains Apache group.
The Southwestern group can be further divided into two subgroups (A) Western and (B) Eastern.
The Western subgroup consists of Western Apache, Navajo, Mescalero, and Chiricahua.
The Eastern subgroup consists of Jicarilla and Lipan.
I. Plains (AKA Kiowa–Apache)
i. Chiricahua proper
ii. Warm Springs
3. Western Apache (AKA Coyotero Apache)
a. Tonto (Northern Tonto, Southern Tonto)
b. White Mountain
c. San Carlos
d. Cibecue (ˀa˙paču)
1. Jicarilla (Apaches De La Xicarilla)
Hoijer’s classification is based primarily on the differences of the pronunciation of the initial consonant of noun and verb stems.
His earlier 1938 classification had only two branches with Plains Apache grouped together with the other Eastern languages (i.e. with Jicarilla and Lipan).
Mescalero and Chiricahua are considered different languages even though they are mutually intelligible (Ethnologue considers them the same language).
Western Apache (especially the Dilzhe’e variety) and Navajo are closer to each other than either is to Mescalero/Chiricahua.
Lipan Apache and Plains Apache are nearly extinct (in fact Lipan may already be extinct).
Chiricahua is severely endangered.
Mescalero, Jicarilla, and Western Apache are considered endangered as well, but fortunately children are still learning the languages although the number of child speakers continues to decline.
Navajo is one of the most vigorous North American languages, but use among first-graders has declined from 90% to 30% in recent years.