breathe

Breathe is the act of taking air into the lungs (inhalation) and expelling it again (exhalation). It is essential for gas exchange, supplying oxygen to the body's tissues and removing carbon dioxide produced by metabolism. The word is commonly used as a verb; the related noun is breath.

Anatomy and mechanics: Air enters through the nose or mouth, passes through the pharynx and larynx to the trachea, then into the bronchi and bronchioles, reaching the alveoli in the lungs. During inhalation, the diaphragm contracts and moves downward while the intercostal muscles expand the chest, creating a negative pressure that draws air in. During exhalation, the diaphragm relaxes and the chest reduces in volume, pushing air out. Gas exchange occurs in the alveoli, where oxygen diffuses into the blood and carbon dioxide diffuses into the air to be exhaled.

Regulation and variation: Breathing is normally controlled automatically by the brainstem, yet it can be influenced by emotion, activity, and environment. Chemoreceptors respond mainly to carbon dioxide levels and, to a lesser extent, oxygen levels, adjusting rate and depth. Resting breathing in healthy adults is typically about 12 to 20 breaths per minute; exercise, fever, altitude, and anxiety increase rate and depth.

Health and context: Good air quality, avoiding smoke and pollutants, supports efficient breathing. Chronic respiratory conditions such as asthma, chronic obstructive disease (COPD), pneumonia, and fibrosis can alter breathing patterns and gas exchange. Breathing techniques are used in medical and wellness contexts to manage stress, exposure to air pollution, and some respiratory conditions, though they should not substitute medical treatment when needed.

Related terms: "breathe" emphasizes the act, while "breath" denotes the air taken in or out. Breath control and deliberate breathing exercises appear in various traditions and therapies, including meditation and pulmonary rehabilitation programs.