Apache languages are tonal languages. Regarding tonal development, all Apache languages are "low-marked" languages, which means that stems with a "constricted" syllable rime in the proto-language developed low tone while all other rimes developed high tone. Other Northern Athabascan languages are "high-marked" languages in which the tonal development is the reverse. In the example below, if low-marked Navajo and Chiricahua have a low tone, then the high-marked Northern Athabascan languages, Slavey and Chilcotin, have a high tone, and if Navajo and Chiricahua have a high tone, then Slavey and Chilcotin have a low tone.