Hypothetical mood is an epistemic mood that signals that the speaker evaluates a proposition as counterfactual, but otherwise possible.
(Lakhota)
The word tkha signals hypothetical mood, as in the following construction (diacritical markings are not reproduced here):
Noonan, Michael. 1985. "Complementation." In Shopen 1985c
Chung, Sandra, and Alan Timberlake. 1985.Tense, aspect, and mood . In Shopen 1985d
Boas, F., and E. Deloria. 1941.Dakota grammar. Memoirs of the National Academy of Science 23(2). Washington, DC: Government Printing Office. 9683101704.