Dyssomnia refers to the problem in getting to sleep or in obtaining sleep of sufficient quality. It is a primary sleep disorder that involve abnormalities in the amount, quality, or
timing of sleep
Moreover, Dysnomias refer to the category of sleep disorders involving difficulties initiating or maintaining sleep. Such disorders are often characterized by problems with getting enough sleep, not sleeping when one wants to, and not feeling refreshed after sleeping.
Other /More definition:
dyssomnia refers to the problem in getting to sleep or in obtaining sleep of sufficient quality.