失眠是指個人呈現出的睡眠困難。失眠最常被認為的跡象和症狀，可以伴隨著多數個睡眠，醫療，精神疾病，持久性難以入睡和/或保持睡眠或睡眠質量差幾個特點。失眠通常跟隨著是清醒時的功能障礙。睡覺時間與年紀.壓力成反比。

Insomnia (or sleeplessness) is an individual's report of sleeping difficulties. Insomnia is most often thought of as both a sign and a symptom that can accompany several sleep, medical, and psychiatric disorders, characterized by persistent difficulty falling asleep and/or staying asleep or sleep of poor quality. Insomnia is typically followed by functional impairment while awake. Sleeping hour is in inverse proportion to age and pressure.