Breathing glossary

What’s in this breathing glossary?

Four groups of terms: the body, the heart and nervous system, the techniques and the research. Within each, terms are in alphabetical order.

What do the body words mean?

Air hunger

The feeling that you can’t get a full, satisfying breath, even when your oxygen is fine. Common with stress and anxiety. More in air hunger and anxiety.

Alveoli

The tiny air sacs deep in your lungs, where oxygen passes into the blood and carbon dioxide passes out. Spontaneous sighs help keep them open.

Breathing rate

How many breaths you take a minute, also called respiratory rate. About 12 to 20 is typical for an adult at rest. More in normal breathing rate.

Carbon dioxide

CO2, the gas you breathe out. Rising carbon dioxide, more than falling oxygen, is what makes you feel the urge to breathe.

Chest breathing

Quick, high breaths that move the upper chest more than the belly. Common when you’re stressed. Compare it with belly breathing in chest breathing vs belly breathing.

Diaphragm

The dome-shaped muscle under your lungs that does most of the work of breathing in. As it flattens, your belly moves out.

Dysfunctional breathing

Breathing patterns that cause symptoms such as breathlessness without a lung or heart problem to explain them: over-breathing, frequent deep sighing or chest-led breathing, for example.

Dyspnoea

The medical word for breathlessness (dyspnea in the US).

Hyperventilation

Breathing more than your body needs, also called over-breathing. It lowers carbon dioxide and can bring light-headedness, tingling and a racing heart. More in how to stop hyperventilating.

Hypocapnia

Lower than normal carbon dioxide in the blood, usually from over-breathing. It’s why fast, deep breathing can make your fingers tingle.

Nasal breathing

Breathing in and out through your nose, which filters, warms and moistens the air. The comparison is in nose breathing vs mouth breathing.

Nitric oxide

A gas made in your sinuses and carried into the lungs when you breathe through your nose. Humming raises it in the nose: about 15-fold in one small study (Weitzberg & Lundberg 2002).

Shallow breathing

Small, quick breaths high in the chest. Usually harmless, often a sign of stress. More in shallow breathing.

Sigh

An extra-large breath your body takes on its own every few minutes, to reopen the alveoli and reset your breathing rhythm. More in why do I sigh so much.

Tidal volume

The amount of air in one ordinary breath at rest: roughly half a litre for an adult.

What do the heart and nervous system words mean?

Autonomic nervous system

The part of your nervous system that runs things without you thinking: heartbeat, digestion, sweating and, mostly, breathing. Its two main branches are below.

Baroreflex

The reflex that keeps your blood pressure steady by nudging your heart rate up or down. At about 6 breaths a minute, it swings in step with your breathing (Lehrer & Gevirtz 2014).

Coherence

The smooth, wave-like heart rhythm you get when you breathe at your resonance pace. It also gives coherent breathing its name.

Fight or flight

The quick stress response: a faster heart, faster breathing, tense muscles. Driven by the sympathetic branch.

Heart rate variability

HRV: the small changes in the time between heartbeats. It tends to be higher when your body is at rest, and slow breathing raises it (Laborde et al. 2022). More in what is HRV.

HRV biofeedback

Breathing at your resonance pace while watching your heart rhythm on a screen, so you can find the pace that makes it swing the most.

Parasympathetic nervous system

The branch of the autonomic nervous system that settles you: a slower heart, digestion, rest. Often called “rest and digest”. More in how to activate your parasympathetic nervous system.

Polyvagal theory

A popular theory linking the vagus nerve to feelings of safety. Many physiologists dispute its core claims, so we use plainer words.

Resonance frequency

The breathing pace at which your heart rhythm swings the most: about 6 breaths a minute for most adults, somewhere between 4.5 and 6.5 (Meehan & Shaffer 2024). Try it here.

Respiratory sinus arrhythmia

RSA: the natural speeding of your heart as you breathe in and slowing as you breathe out. It’s normal and healthy, and largest when you breathe slowly.

Rest and digest

The settled state of the parasympathetic branch: the opposite of fight or flight.

RMSSD

A common HRV measure, short for root mean square of successive differences. It mainly reflects the vagus nerve’s effect on your heart, and it’s one of the figures heart-rate apps and wearables report.

Sympathetic nervous system

The branch that gears you up for action: a faster heart, quicker breathing, more alert.

Vagal tone

How strongly the vagus nerve is slowing your heart at rest, estimated from heart rate variability. Higher vagal tone tends to go with a body at ease.

Vagus nerve

The main nerve of the parasympathetic system, running from your brainstem to your heart, lungs and gut. Breathing influences it indirectly; you can’t switch it on. More in vagus nerve reset.

What are the breathing techniques called?

4-7-8 breathing

In for 4, hold for 7, out for 8, popularised by Dr Andrew Weil for winding down. Full guide: 4-7-8 breathing.

Alternate nostril breathing

Nadi shodhana in yoga: breathing in through one nostril and out through the other, switching sides. Full guide: alternate nostril breathing.

Bhramari

Humming bee breath: a slow breath in, then a soft hum on the long breath out. Full guide: humming bee breath.

BOLT score

Body Oxygen Level Test: the seconds you can comfortably pause after a normal breath out. Popular, but unvalidated. More in CO2 tolerance and the BOLT score.

Box breathing

In for 4, hold for 4, out for 4, rest for 4: four equal sides. Also called square or tactical breathing. Full guide: box breathing.

Breath of fire

Rapid, rhythmic breathing through the nose, from Kundalini yoga, about 2 or 3 breaths a second: in and out for the same length, the belly pumping each out-breath and the in-breath following by itself. A close cousin of kapalabhati, yoga’s short, sharp out-breaths. An intense practice we describe but don’t teach.

Breathwork

A broad modern word for breathing on purpose, from gentle paced breathing to intense methods. More in what is breathwork.

Buteyko method

A method of lighter, slower nose breathing, often taught for asthma, built on the idea that many people over-breathe. Full guide: Buteyko breathing.

CO2 tolerance

A popular name for how comfortably you sit with the urge to breathe as carbon dioxide rises. Usually estimated with a breath-hold test.

Coherent breathing

Slow, even breathing at about 6 breaths a minute: 5 seconds in, 5 out. Also called resonant breathing.

Control pause

The Buteyko method’s name for the same pause the BOLT score measures.

Cyclic sighing

Repeating the physiological sigh for a few minutes: two breaths in, one long breath out, again and again.

Diaphragmatic breathing

Belly breathing: breathing low, so the diaphragm does the work and your belly moves more than your chest. Full guide: diaphragmatic breathing.

Extended exhale

Any breath where the out-breath is longer than the in-breath, such as 4-6 breathing.

Holotropic breathwork

Fast, deep breathing for an hour or more, used in workshops to reach altered states. Intense: described, not taught, in types of breathwork.

Kumbhaka

The yoga word for a breath hold, after breathing in or after breathing out. Breathform keeps the words plain: a hold after the in-breath, a rest after the out-breath.

Mouth taping

Taping the lips at night to keep breathing nasal. The evidence is thin. More in is mouth taping safe.

Paced breathing

Breathing to a set count or guide: a timer, a tone, an animation or a tap on your wrist.

Physiological sigh

A sigh on purpose: two breaths in through the nose, a full one and a short top-up, then one long breath out. Full guide: physiological sigh.

Pranayama

The breath practices of yoga. The Sanskrit is usually translated as extending or controlling the breath. Full guide: pranayama.

Pursed-lip breathing

Breathing out slowly through softly pursed lips, as if cooling soup. Full guide: pursed-lip breathing.

Slow breathing

Breathing at 4 to 10 breaths a minute, most often about 6 (Russo et al. 2017). What it does, and doesn’t do, is in slow breathing benefits.

Ujjayi

Ocean breath: slow breathing with the throat gently narrowed, so each breath makes a soft rushing sound. Full guide: ujjayi breathing.

Wim Hof method

Rounds of fast, deep breathing followed by long breath holds, often paired with cold exposure. Never practise breath holds in or near water.

What do the research words mean?

Active control

A comparison group that also does something, such as a different breathing practice. Beating an active control is harder, and more convincing, than beating no treatment.

Effect size

How big a difference is, in standard units. Small, medium and large are the usual labels, so you can compare studies that measured different things.

Evidence levels

Breathform’s three labels for how much research backs a technique: well studied, some evidence, and early or traditional. Every study is on our science page.

Meta-analysis

A study that pools the results of many studies into one combined estimate.

Placebo

A comparison that looks like the real thing but shouldn’t work. In breathing research, it’s often a breathing practice at a normal pace.

Randomised controlled trial

RCT: a study where people are assigned to groups by chance, so the groups differ only in what’s being tested. The fairest single test.

Self-reported

Measured by asking people how they feel or slept, rather than with a device. Useful, but more open to expectation than a heart-rate reading.

Systematic review

A review that searches for every study on a question, using set rules, and weighs them together. A narrative review, by contrast, is an expert’s summary without those rules.

Every study on this page (5)

• Weitzberg & Lundberg, 2002: Humming raised nitric oxide in the nose 15-fold compared with breathing out quietly, in 10 healthy people; health effects weren't tested.
• Lehrer & Gevirtz, 2014: Heart rate swings most at around six breaths a minute; this review says a blood-pressure reflex is the likeliest reason.
• Laborde et al., 2022: Across 223 studies, slow breathing raised heart-rhythm signs of calm, during practice and after, though that alone doesn't prove a health benefit.
• Meehan & Shaffer, 2024: In two small studies at six breaths a minute, breathing out longer than in made no difference to heart-rhythm measures.
• Russo et al., 2017: An overview of research in healthy people suggests slow breathing affects the heart, lungs and nervous system; more study is needed.

Questions people ask

What is vagal tone?

It’s a way of describing how strongly the vagus nerve is slowing your heart at rest. Nobody measures the nerve directly: vagal tone is estimated from heart rate variability, especially the part that rises and falls with your breathing. Higher values tend to go with a body at ease. Slow breathing raises them for a while, during and after practice.

What is resonance frequency breathing?

Breathing at the pace that makes your heart rhythm swing the most, which for most adults is about 6 breaths a minute, somewhere between 4.5 and 6.5. In practice, that’s about 5 seconds in and 5 seconds out. It’s also called resonant or coherent breathing, and it’s the pace used in most slow-breathing research.

What’s the difference between breathwork and pranayama?

Pranayama is the breath practice of yoga, centuries old, with its own named techniques such as nadi shodhana and bhramari. Breathwork is a broad modern word for any breathing on purpose, which includes gentle paced breathing, some pranayama and intense methods like holotropic breathwork. All pranayama is breathwork; not all breathwork is pranayama.

What is a breath hold called?

In medicine, a pause in breathing is called apnoea (apnea in the US). In yoga, a held breath is kumbhaka: after breathing in, or after breathing out. Breathform says hold for a pause after the in-breath and rest for a pause after the out-breath.