15 Terms to Expand Your Sleep Vocabulary

Bruxism is the unconscious, involuntary act of clenching or grinding one’s teeth while asleep. It often occurs during periods of stress. Bruxism comes from the Greek word "brychein," which means gnashing of teeth. It can lead to tooth damage, jaw pain, and headaches. It may be a sign of sleep apnea.

Cataplexy is the sudden loss of muscle tone often triggered by intense emotions such as laughter, surprise, or anger. It causes weakness and even temporary paralysis, sometimes resulting in a collapse in posture. It is one of the four cardinal symptoms of narcolepsy.

Coined by Franz Halberg in 1959 and from the Latin meaning “about a day,” circadian refers to numerous phenomena (especially biological rhythms) that have an interval length of approximately 24 hours. It may be used in reference to circadian rhythm sleep disorders.

More commonly known as bedwetting, enuresis is the involuntary loss of urine (usually during deep sleep) beyond an age when voluntary control should be present. It most often affects children but may impact younger adolescents.

Found deep within the temporal lobe of the brain, the hippocampus is a seahorse-shaped structure that controls many important brain functions including emotions and learning. It is important for memory processing during sleep.

Hypopnea refers to shallow breathing or a transient reduction of airflow that occurs while asleep and lasts for at least 10 seconds. It is less severe than apnea, which refers to a more complete loss of airflow. Hypopnea may occur due to a partial obstruction of the upper airway (typically the soft palate or tongue collapsing into the throat). These episodes may trigger a drop in the blood oxygen level or brief arousal or awakening.

Jet lag is a temporary condition that is caused by rapid travel across time zones—as may occur with jet trips—and may leave an individual experiencing fatigue, insomnia, nausea, or other symptoms as a result of the internal circadian rhythm, or biological clock, being misaligned with local time.

Macroglossia refers to an abnormally large tongue that may obstruct the airway and lead to sleep apnea. In children, macroglossia may be associated with Down’s syndrome, glycogen storage disease, or congenital hypothyroidism.

Microsleep is a brief, fleeting episode of sleep that lasts from a fraction of a second up to 10 seconds. It frequently occurs in sleepy people who are trying to remain awake. These episodes are uncontrollable and can lead to accidents involving cars or heavy machinery.

Parasomnias are sleep disorders characterized by abnormal sleep behaviors. The word comes from Latin and means “around sleep.” Parasomnias involve unconscious complex, semi-purposeful, and goal-directed behaviors. These may include sleep terrors, sleepwalking, sleep eating, sleep sex, rapid eye movement (REM) behavior disorder, or any number of potential behaviors while the person remains asleep.

Pavor nocturnus is an episodic emotional disturbance that occurs in sleep and typically affects young children. The episodes may include screaming, moaning, gasping, panic, and anxiety. Unlike nightmares, these episodes occur in non-rapid eye movement (REM) or slow-wave sleep. One of the parasomnias, an individual experiencing pavor nocturnus is not fully conscious and usually does not remember the episode in the morning.

Retrognathia is a small or recessed jaw (either the upper jaw called the maxilla or the lower jaw called the mandible) that may predispose to obstruction of the airway. This may lead to sleep apnea. It is sometimes corrected through surgery which moves the jaw forward.

Sleep architecture represents the structure of sleep and is generally composed of a somewhat cyclical pattern of the various non-rapid eye movement (NREM) and rapid eye movement (REM) sleep stages. It can be summarized with a chart called a hypnogram.

Somniloquy is the act or habit of talking in one's sleep.

From the German for “time giver,” zeitgeber refers to any external cue that can entrain (or reset) the time-keeping system of organisms. In humans, this circadian system, or biological clock, is located in the suprachiasmatic nucleus within the hypothalamus of the brain. This system is affected by zeitgebers. These cues follow a periodic pattern. The strongest zeitgeber is the natural pattern of light and darkness.