• A sensation of discomfort with breathing.
  NICHD Pediatric Terminology
  U.S. National Cancer Institute, 2021
• An uncomfortable sensation of difficulty breathing. It may present as an acute or chronic sign of an underlying respiratory or heart disorder.
  NCI
  U.S. National Cancer Institute, 2021
• Difficult or labored breathing. Dyspnea is a subjective feeling only the patient can rate, e.g., on a Borg scale.
  Human Phenotype Ontology (HPO)
  The Human Phenotype Ontology Project, 2025
• Difficult, painful breathing or shortness of breath.
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• Difficulty breathing or shortness of breath.
  Harvard Dictionary of Health Terms
  Harvard Medical Publishing, 2011
• Includes dyspnea on exertion, dyspnea at rest, orthopnea, and paroxysmal nocturnal dyspnea.
  CDISC Terminology
  Clinical Data Interchange Standards Consortium (CDISC), 2021
• Labored or difficult breathing associated with a variety of disorders, indicating inadequate ventilation or low blood oxygen or a subjective experience of breathing discomfort.
  CRISP Thesaurus
  National Institutes of Health, 2006
• A disorder characterized by an uncomfortable sensation of difficulty breathing.
  Common Terminology Criteria for Adverse Events
  U.S. National Institutes of Health, 2021
• Dyspnea is unpleasant or uncomfortable breathing. It is experienced and described differently by patients depending on the cause.
  Merck Manuals
  Merck & Co., Inc., 2025