An unconscious state is a condition in which a person is not aware of their surroundings or unable to respond to stimuli. COMA, SENSELESSNESS, anesthesia, sleep, FAINT, and STUPOR are all examples of an unconscious state. COMA is a deep, prolonged state of unconsciousness caused by severe injury or illness. SENSELESSNESS is a lack of awareness or understanding. Anesthesia is a drug-induced loss of sensation or consciousness. Sleep is a natural, reversible state of unconsciousness. FAINT is a brief loss of consciousness due to a lack of oxygen to the brain. STUPOR is a state of near-unconsciousness in which a person is unresponsive to external stimuli.