The vowel alternation may involve more than just a change in vowel quality. In Athabaskan languages, such as Navajo, verbs have series of stems where the vowel alternates (sometimes with an added suffix) indicating a different tense-aspect. Navajo vowel ablaut, depending on the verb, may be a change in vowel, vowel length, nasality, and/or tone. For example, the verb stem "-kaah/-ką́" "to handle an open container" has a total of 16 combinations of the 5 modes and 4 aspects, resulting in 7 different verb stem forms (i.e. "-kaah", "-kááh", "-kaał", "-kááł", "-ka’", "-ká", "-ką́").