Here are definitions of sleep-related terms:
Chronotherapy: A behavioral technique in which bedtime is gradually adjusted; used in cases when the patient's sleep-wake pattern is out of synch with the external environment.
Circadian rhythms: Biological rhythms that include the internal clock which influences when, how much, and how well people sleep.
Cognitive therapy: In some cases of insomnia, this therapy includes interventions that are meant to help people identify and correct inappropriate thoughts and beliefs that may contribute to their sleep problems.
Mixed sleep apnea: A combination of central sleep apnea and obstructive sleep apnea.
Multiple sleep latency test (MSLT): Test that assesses the severity of sleepiness by measuring the speed of falling asleep.
Narcolepsy: A neurological condition in which people experience excessive daytime sleepiness, cataplexy, sleep paralysis, hallucinations, and intermittent, uncontrollable sleep attacks during the day.
Non-Rapid Eye Movement (NREM) sleep: One of the two basic states of sleep; consists of stages 1, 2 (light sleep) and 3, 4 (deep sleep).
Obstructive sleep apnea (OSA): The most common kind of sleep apnea. It is caused by a blockage of the upper airway that causes the body to struggle to get air.
Periodic Limb Movement Disorder (PLMD): A disorder in which rhythmic jerking of the legs interrupts sleep, causing insomnia and/or excessive daytime sleepiness.
Parasomnias: Abnormal behaviors during sleep that interrupt sleep and can result in injury, insomnia, and/or excessive daytime sleepiness.
Polysomnography: A test that records aspects of sleep (for example, the amount of NREM and REM sleep, number of arousals) and a variety of body functions during sleep, including breathing patterns, heart rhythms, and limb movements.
Progressive Muscle Relaxation (PMR): Relaxation method that involves tensing and relaxing muscles of the body in a given order, ultimately to achieve relaxation of the whole body; useful in some cases of insomnia.
Rapid Eye Movement (REM) sleep: One of the two basic states of sleep. REM sleep, also known as dream sleep, is characterized by rapid eye movements, and more irregular breathing and heart rate compared to NREM sleep, the other basic state of sleep.
Sleep apnea: Sleep disorder that occurs when a person's breathing temporarily stops during sleep.
Sleep hygiene: Practices, habits, and environmental factors that are important for getting sound sleep.
Sleep paralysis: Symptom of narcolepsy; involves the temporary inability to move or speak while falling asleep or waking up. May also be caused by sleep deprivation, irregular sleep patterns, family history, and other causes.