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Your A to Zzzzz's guide to the wonderful world of sleep
sleep glossary: get down with the sleep slang

Want to get clued up on all things sleep? Or feeling a bit baffled by something we’ve said? You’ve come to the right place. Our sleep glossary has everything you need to become a sleep wellness pro. Pub quiz here you come.

top sleep words and what they mean


A hormone that’s associated with stress levels, causing increased circulation and faster breathing. Raised adrenaline before bed can negatively impact sleep or make it harder to nod off.

body clock

The body’s internal clock that helps to coordinate its functions, including sleep. The body clock loves following a pattern, which is why so many of us still wake up at 7am on a weekend.

circadian rhythms

Biological rhythms inside our body that influence when, how much and how well we sleep. The body clock is a circadian rhythm.


A pattern of sleeping and waking activity that reflects your personal circadian rhythm. Examples of chronotypes include morning larks, grumpy geese and night owls. Take the early bird quiz to find out which one you are.

cognitive function

Our ability to learn, think, remember and make decisions. Poor or little sleep can lead to rubbish cognitive function, which is why we’re more likely to eat junk when we’re running on empty.


The body’s primary stress hormone which can lead us into a fight or flight response. Too much cortisol in the body can impact our sleep quality and health.


The happy hormone that’s an important part of your brain’s reward system. It’s associated with pleasurable sensations, food, learning, memory and our motor system function.


Instances of images, ideas, emotions and circumstances that happen in the mind during REM sleep. Take our dream quiz to find out what your dreams say about you.


That feeling of tiredness or weariness that doesn’t get better with sleep.

fragmented sleep

Repeated waking up that causes interrupted and poor sleep.


Difficulty falling or staying asleep. In a nutshell: sleeplessness.


A hormone that regulates our sleeping and waking cycles. We normally produce it in response to darkness, signalling to our brain that it’s time for sleep. Some foods contain melatonin, making them great for sleep.


A chemical that allows our brain cells to communicate with each other. Functions like sleep and wakefulness are affected by changes in neurotransmitter levels.

non-REM sleep

One of 2 types of sleep and the opposite to REM (rapid eye movement) sleep. The time we spend in NREM is highest during the first half of a sleep period. During NREM, sleep is dreamless, breathing and heart rate are slow and regular, and blood pressure is low.

optimum sleep

The average amount of sleep we need each night. This isn’t a ‘one size fits all’. Our routine calculator can help you work out your optimum sleep.

parasympathetic nervous system

Responsible for the body’s rest and digest response which happens when we’re relaxed, resting or eating. It is the opposite to the sympathetic nervous system.

REM sleep

Rapid eye movement (REM) is one of 2 types of sleep. Known for intense dreaming, this is the stage of sleep with the most brain activity and usually occurs in the second half of a sleep period.


Physical or mental exercises that promote dynamic relaxation and rest, encouraging you to be more present and step out of “thinking mode” into “doing mode”. It’s a form of mindfulness.

sleep cycle

A progression through individual sleep stages including NREM and REM sleep. On average, we go through 4-6 sleep cycles per night, lasting between 70 and 120 minutes each.

sleep hygiene

Practices, habits and environmental factors that impact the quality of sleep. Healthy sleep hygiene can help you to get the top notch sleep you need to rise and shine.

sleep inertia

Feelings of grogginess and sleepiness that persist throughout the day instead of just when you wake. Otherwise known as fatigue.

sleep quality

How an individual rates their sleep. It usually depends on how well they slept, how much sleep they got and how refreshed they feel when they wake up.

sleep pattern

Your schedule of bedtimes, wake times and naps.

sympathetic nervous system

The system that controls the body’s response to dangerous or stressful situations - also known as our fight or flight response. It’s responsible for boosting our alertness, increasing heart rate and sending extra blood to the muscles.