<unk> s are a family of sleep disorders affecting the timing of sleep. People with<unk> s are unable to sleep and wake at the times required for normal work, school, and social needs. They are generally able to get enough sleep if allowed to sleep and wake at the times dictated by their body clocks. Unless they have another sleep disorder, their sleep is of normal quality.
Humans have biological<unk> s, known as<unk><unk> s, which are controlled by a biological clock and work on a daily time scale. Due to the<unk>  clock, sleepiness does not continuously increase as time passes. A person's desire and ability to fall asleep is influenced by both the length of time since the person woke from an adequate sleep, and by internal<unk><unk> s. Thus, the body is ready for sleep and for wakefulness at different times of the day.
Circadian rhythm sleep disorder
Shift work sleep disorder
Delayed sleep phase syndrome
Non-24-hour sleep-wake syndrome
Sleep hyperhidrosis
Advanced sleep phase syndrome
Sleep disorder
Sleep Apnea