what is sleep definition

What Is Sleep Definition Actually?

What is sleep definition? The dictionary says that sleep is ‘a condition of body and mind that typically recurs for several hours every night, in which the nervous system is relatively inactive, the eyes closed, the postural muscles relaxed, and consciousness practically suspended.’ But we now know that there is more to sleep than meets the eye.

For many years, medical experts believed that sleep was just a passive activity. They thought it was when both your body and mind took a breather from the world or a rest.

Yet, as it turns out, sleep is when your body may be resting. But your brain is hard at work carrying out multiple activities that are necessary to your life.

In short, the better your sleep, the better the quality of your life will be in general. Add to that the fact that we spend a third of our time sleeping. That should be enough to get you motivated to get the best quality sleep that you can.

what is sleep definition

Keep reading to find out all you can about sleep and how it affects our overall well-being.

What Is Sleep Definition?

Sleep is a state where awareness of environmental stimuli is reduced. Sleep is different from states of coma, hibernation, and death by the fact that it can be rapidly reversed.

Dr. Rafael Pelayo, MD, a sleep specialist at the Stanford Sleep Medicine Center in Redwood City, defines sleep as, “…a natural restorative, physiological process.”

We also get a similar definition from sleep experts at Harvard Medical School of Sleep Medicine. Yet, they take it a step further by characterizing sleep as the following:

  • A process where you’re less likely to be responsive to external stimuli.
  • A state of consciousness that can be easily reversed.
  • A physiological state that affects brain wave activities, blood pressure, and temperature.
  • A vital bodily process that maintains healthy physiological and mental functions.

The Different Stages Of Sleep

As you sleep, your brain goes back and forth between two stages: (rapid-eye movement) REM and non-REM. Each one lasts about 90 minutes.

The first part of the sleep cycle is non-REM, which is made up of three phases:

  1. The first phase is when you’re just falling asleep.
  2. The second is light sleep is when your body temperature drops and your heart rate slows down.
  3. The third is deep sleep is the most restorative when your heartbeat slows down the most. This is also known as slow-wave sleep. It is quite difficult to awaken somebody in this state of sleep.

After that, comes the REM sleep cycle. This is when your eyes dart quickly from side to side because brain activity is at its peak. It’s also when most of your dreams happen, especially those you remember when you wake up. Your heart rate increases slightly, while your breathing becomes quicker and irregular.

Another interesting fact: during REM sleep, your arms and legs are temporarily paralyzed. Experts believe this is our body’s way of protecting itself in case you decide to act out any of your dreams.

The two most important stages are deep sleep and REM sleep. They play vital roles when it comes to memory consolidation and boosting cognitive functions.

Why Is Sleep Important?

Getting good-quality sleep each night is vital for maintaining a healthy lifestyle. Never look at sleep as a luxury or an indulgence as our society would like us to believe.

During sleep, your body and mind sift through everything you went through that day. They throw out what you don’t need and permanently store the important information.

When you’re sleep-deprived, you go through the day unable to focus and your attention span is short. Not getting enough sleep also affects many physiological processes. So, you end up feeling worn out and exhausted the whole day.

Here are some of the other benefits of getting good-quality sleep.

  • You wake up feeling refreshed and energized.
  • Sleep boosts your immune system.
  • Your whole body needs sleep to stay healthy and disease-free.
  • Sleep helps regulate emotions and manage stress.
  • Memories are reorganized during sleep.
  • Sleep helps restore cognitive functions while elevating focus and concentration levels.

How Many Hours Of Sleep Does A Person Need?

National Sleep Foundation guidelines advise that healthy adults need between seven and nine hours of sleep per night. Babies, young children, and teens need even more sleep to enable their growth and development.

People over 65 should also get seven to eight hours per night.

When it comes to deep sleep, the average adult needs between 1.6 and 2.25 hours of deep sleep a night. Newborns and babies need around 2.4 to 3.6 hours of deep sleep; children ages one to five need around 2.2 to 2.8 hours of deep sleep, and teenagers need around 1.7 to 2 hours of deep sleep.

How Can We Get A Good Night’s Sleep?

How much sleep you should get differs from one person to the next. It factors in age, gender, health condition, and even genes.

Yet, according to the National Sleep Foundation (NSF), adults should aim to get anywhere between seven to nine hours of good-quality sleep each night.

Researchers have come up with several strategies to help you get a peaceful, full night’s sleep. You can turn these strategies into goals, then, eventually, habits. All you have to do is practice them each day and be consistent.

Let’s check them out.

Make Your Bedroom A Sleep-Friendly Zone

For starters, you should dim the lights about half an hour before going to bed. Make sure the room is at a pleasant temperature.

what is sleep definition

Your sheets and duvet should be snug and cozy. Another important point to factor in is your mattress and pillow. They should be firm, yet comfortable to help you fall asleep faster.

Establish A Regular Bedtime Routine

Create a routine where you go to bed and wake up at the same time every day. Try to be consistent, even on weekends. Rather than watch TV, read a book to wind down.

After a few days, your body will get the message and engage your body’s circadian rhythm. When this rhythm is in sync, you’ll fall asleep easier and wake up feeling more refreshed.

Yet, if it’s out of whack, you’ll feel the same fogginess and drowsiness typically associated with jet lag.

Avoid Stimulants And Large Meals In The Evening

Medical experts recommend that you avoid drinking or consuming stimulants for about four to six hours before bedtime. Remember that caffeine has a half-life of four to five hours. In other words, your body takes about five hours to get rid of only half the amount of caffeine you consumed.

Just as detrimental to sleep as caffeine, heavy meals can make you feel uncomfortable. Rather than start to relax, your digestive system will work overtime to digest all the food you consumed. This will also make it harder to fall asleep.

Ban Screens From Your Bed

The light that comes from cell phones and computer screens is detrimental to sleep. Your brain mistakes this light for sunlight. As a result, it blocks the release of melatonin; the hormone that signals your brain to sleep.

One thing we can all agree on is that sleep is an essential function that allows your body and mind to recharge, leaving you refreshed and alert when you wake up. Healthy sleep also helps the body remain healthy and stave off diseases. Without enough sleep, the brain cannot function properly.

Here are some more tips to help you to sleep better.

Please comment below if you can add to this article – what is sleep definition.


  1. Thanks for sharing this amazing article. I found it to be a very interesting read indeed as it is well written and informative. For the past few years, I have been sleeping in bouts whenever I can get the chance. I find that trying to lie down to purposely sleep only makes me hyper. So i end up dosing here and there.

  2. I believe that sleep is the foundation of almost everything health-related—your mental, physical and emotional health. I know I am more likely to eat poorly, skip exercise and interact poorly with others when I have had six hours of sleep or less. I generally aim for 7-8 hours and sleep 8-10 on the weekends.

  3. Hmmm… I enjoyed your article about sleep definition. As I have some sleep issues these days, I will take your advice into account. I already eat light dinners and I avoid stimulants. However, I still need to ban electronic devices from my bedroom. I am literally addicted to my iPad because I enjoy watching videos in my bed. 

  4. Thanks for sharing this amazing article, I found it very informative. I firmly believe that healing also takes place during sleep, a good rest and quality sleep will definitely lower stress levels.  I feel sorry for people that are shift workers, people that have to work during the night and sleep during daytime. Those that are on a permanent night shift may get used to sleeping during daytime but shift workers that change shifts on a regular basis may suffer with impaired alertness and performance due to sleep loss and circadian misalignment, biological body rhythms get disturbed which can cause so many other health problems and stresses.  Great article, thank you.          

    1. Thanks for stopping by Carola and yes you are quite right, especially about the body taking time to heal as we sleep.

  5. I did not realize there were four stages involved in sleep. I knew of two, deep and rem. It is interesting to note that without all four stages of sleep we are harming ourselves, especially our immune system. 

    I knew that setting a regular schedule for sleep is essential and that drinking caffeine would affect your sleep but I did not know that eating a large meal would disturb your sleep pattern and make it more difficult to reach deep sleep. With this new knowledge, I should be able to change my schedule and start to have a better sleeping pattern.


    1. I think that there is still so much that scientists are discovering all the time about sleep, and it is scary what lack of it can do to our bodies.

      Good luck with your own sleep schedule.

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