Sleep debt or sleep deficit is the cumulative effect of not getting enough sleep. A large sleep debt may lead to mental and/or physical fatigue.
There are presumed to be two kinds of sleep debt, one of them is caused by partial sleep deprivation or total sleep deprivation. Partial sleep deprivation occurs when a person or a lab animal sleeps too little for many days or weeks. Total sleep deprivation means being kept awake for days or weeks. There is debate in the scientific community over the specifics of sleep debt, and it is not considered to be a sleep disorder.