Child sleep glossary
Sleep advice is full of jargon, and most of it is never explained. These are the terms you will meet in our guides and everywhere else, each defined in plain language, with the page to read if you want the detail.
Last reviewed: 2026-09-17
Start here
- Wake window and sleep pressure explain most nap and bedtime problems.
- A false start and a split night look similar at 10pm but have different causes.
- A regression is a developmental change in sleep, not a behaviour problem.
How the terms fit together
Most sleep problems are a timing problem wearing a costume. Sleep pressure builds through the wake window; if bedtime lands before enough has built, you get a false start or a split night. If it lands too far after, you get overtiredness and a 5am start. A sleep association decides whether your child can get back to sleep alone when a sleep cycle ends. A regression temporarily changes how much sleep they need, which throws all of the above out for a few weeks.
If you want the numbers for your child's age rather than the vocabulary, the wake window calculator gives them in about a minute.
Terms A–Z
- Circadian rhythm
- The roughly 24-hour internal clock that tells the body when to be alert and when to sleep. It is set mainly by light and by consistent timing, and it is not fully developed in newborns — which is why a very young baby has no reliable day and night.
- Drowsy but awake
- Putting a child down while they are sleepy but not yet asleep, so that falling asleep happens in the cot rather than in your arms. It is the mechanism behind most gentle settling approaches.
- False start
- A child falls asleep at bedtime, then wakes fully 30 to 60 minutes later, often distressed. Usually caused by too little sleep pressure at bedtime, an overlong final wake window, or falling asleep only with help.
- Overtiredness
- The state where a child has been awake too long and stress hormones rise, making it harder — not easier — to fall asleep. It typically looks like a wired, hyperactive child at bedtime and shows up later as early waking.
- Sleep association
- Whatever conditions a child has learned to need in order to fall asleep: feeding, rocking, a hand on the back, a specific song. Associations are not harmful in themselves; they cause night waking only when the child cannot recreate them alone at 2am.
- Sleep cycle
- One full pass through light sleep, deep sleep and REM. In infants a cycle lasts roughly 40 to 50 minutes, which is why so many naps end abruptly at the 45-minute mark.
- Sleep pressure
- The biological drive to sleep that builds during every hour awake and discharges during sleep. Too little pressure at bedtime means a child cannot fall asleep; too much means they are overtired and cannot either.
- Sleep regression
- A temporary period, usually one to six weeks, where an established sleeper starts waking, resisting bedtime or refusing naps, driven by a developmental change rather than by anything you did. Common points are around 4, 8, 12 and 18 months and 2 years.
- Split night
- A long stretch of being wide awake in the middle of the night — often one to three hours — with the child calm rather than distressed. Usually a sign of too much total daytime sleep or too early a bedtime for their current sleep need.
- Wake window
- The length of time a child can comfortably stay awake between sleeps. It lengthens with age, from under an hour in the newborn weeks to several hours by toddlerhood, and getting it wrong by 30 minutes is enough to ruin a nap.
- Nap transition
- The period when a child drops from one number of naps to the next — three to two, two to one, one to none. Transitions are messy for two to six weeks because the new schedule does not fit until sleep need catches up.
- Early rising
- Waking for the day before 6am and being unable to resettle. Most commonly caused by too-early bedtime, too much daytime sleep, too long a final wake window, or light in the room.
- Bedtime resistance
- Delay tactics, protests or repeated requests at bedtime, most common in toddlers and preschoolers. Usually a mix of mistimed bedtime relative to sleep pressure, and bedtime being the only place autonomy can be tested.
- Sleep onset latency
- How long it takes to fall asleep once settled. Around 15 to 20 minutes is typical; under five minutes suggests overtiredness, and over 40 suggests bedtime is too early.
- Sleep training
- Any structured approach to teaching a child to fall asleep independently, ranging from gradual parental withdrawal to timed checks. Not appropriate before 16 weeks, and not the only route to better sleep — timing changes fix a large share of problems on their own.
Quick answers
What is a wake window?
A wake window is the length of time a child can comfortably stay awake between sleeps. It grows with age — under an hour in the newborn weeks, four to six hours before bedtime by age three. Getting it 30 minutes wrong is enough to cause a failed nap or a bedtime battle.
What is sleep pressure?
Sleep pressure is the biological drive to sleep that accumulates during every hour a child is awake and discharges while they sleep. A successful bedtime is simply bedtime landing at the point where sleep pressure is high enough to fall asleep but not so high that the child has become overtired.
What is the difference between a false start and a split night?
A false start is waking fully 30 to 60 minutes after falling asleep at bedtime, usually distressed. A split night is a long calm period awake in the middle of the night, often one to three hours. A false start usually means bedtime timing or settling; a split night usually means too much total sleep across 24 hours.
Is a sleep regression a real thing?
Yes, in the sense that established sleepers reliably get worse for one to six weeks around specific developmental changes — commonly 4, 8, 12 and 18 months and 2 years. It is driven by brain and motor development, not by anything a parent did wrong, and it resolves.
Put the vocabulary to work
Get the actual numbers for your child's age and a plan you can start tonight, from $45.