1. Sleep disorders characterized by a disturbance in the amount, quality, or timing of sleep: Tom decided not to drink any more coffee because it apparently caused his dyssomnia and so he could not sleep through the night.
2. Any disturbances of normal sleep or rhythm pattern: Sharon's house was next to the railroad tracks which caused her to have dyssomnia because she never got used to the noises of trains traveling during the night.
3. Any disturbance involving the amount, quality, or timing of sleep: Timothy's stress with his boss at work made him have headaches and he became quite nervous. After going to his doctor, because he was getting so little sleep, his condition was diagnosed as dyssomnia and he was encouraged to get a less stressful job.
3. Etymology: from Greek dys-, "bad, ill, impaired, defective" + Latin -somnia, "sleep".