1) Definition Sleep is a naturally recurring state of relatively suspended sensory and motor activity, characterized by total or partial unconsciousness and the inactivity of nearly all voluntary muscles. Human sleep on average a third party of his existence. Sleep guarantees our good physical and psychic health.
The quantity of sleep necessary for each depends on the supplied activity, on the hardness of the working conditions.

2) Duration of sleep The amount of sleep that a person needs to function in a normal manner depends on several factors, including age. As individual become older, sleep duration decrease
Infants sleep most of the day; teenagers usually need about 9 hours a day; and adults need an average of 7 to 8 hours a day.
Although older adults require about as much sleep as younger adults, they usually sleep for shorter periods. It a result of other factors, such as medications that are commonly used by older people.

3) Utility of sleep For instance, certain stages of sleep are indeed for us to feel well rested and energetic the next. Your brain stays active throughout sleep, but different things happen during each stage. day, and other stages help us learn or make memories. In brief, a number of vital tasks carried out during sleep help maintain good health and enable people to function at their best.
The sleep has a role on the performance, mood, and health. We need sleep to think clearly, react quickly, and create memories. In fact, the pathways in the brain that help us learn and remember are very active when we sleep. Studies also find that when you lack sleep, you are more likely to make bad decisions and take more risks. This can result in lower performance on the job or in school and a greater risk for a car crash. Sleep also affects mood. Insufficient sleep can make you irritable and is linked to poor behavior and trouble with relationships, especially among children and teens. Sleep is also important for good health.