• A condition marked by drowsiness and an unusual lack of energy and mental alertness. It can be caused by many things, including illness, injury, or drugs.
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• A general state of sluggishness, listless, or uninterested, with being tired, and having difficulty concentrating and doing simple tasks. It may be related to DEPRESSION or DRUG ADDICTION.
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2021
• A profound lack of mental and physical energy.
  NICHD Pediatric Terminology
  U.S. National Cancer Institute, 2021
• A state of disinterestedness, listlessness, and indifference, resulting in difficulty performing simple tasks or concentrating.
  Human Phenotype Ontology (HPO)
  The Human Phenotype Ontology Project, 2021
• Decreased consciousness characterized by mental and physical inertness.
  NCI Thesaurus
  U.S. National Cancer Institute, 2021
• Experience of decreased consciousness characterized by mental and physical inertness.
  ACC/AHA Clinical Data Terminology
  American College of Cardiology and American Heart Association , 2020
• (lethargic) Characterized by a lack of vitality or energy.
  NCI Thesaurus
  U.S. National Cancer Institute, 2021
• A disorder characterized by a decrease in consciousness characterized by mental and physical inertness.
  Common Terminology Criteria for Adverse Events
  U.S. National Institutes of Health, 2021
• Lethargy, in medicine, a morbid condition of deep and lasting drowsiness from which the sufferer can be aroused only with difficulty and temporarily. It is a symptom of various disorders, such as sleeping sickness (African trypanosomiasis) and encephalitis...
  Encyclopedia Britannica
  Encyclopedia Britannica, Inc., 2020