Dyspnea (Latin dyspnoea, Greek dyspnoia from dyspnoos - short of breath) is perceived difficulty breathing or pain on breathing. It is a common symptom of a great many disorders, including emphysema, COPD, broken ribs, lung cancer, malignant hypertension, and so forth. Dyspnea may be due, as can be seen, to disorders within the lungs themselves, to disorders in the ribcage, to disorders in adjacent organs, to nervous system disorders, or to drugs and toxins.

Other terms for breathing malfunctions include tachypnea, which is too-rapid breathing, and bradypnea, which is too-slow breathing.