Unconsciousness Someone who is unconscious is not sleeping. Rather, an unconscious person is hard to rouse or can't be made aware of his or her surroundings.
Unconsciousness is caused by illness, injury or emotional shock.
There are many levels of unconsciousness. Some are more serious than others. Examples are fainting or blacking out. The victim is incoherent when roused. A person in a coma, for example, can be motionless and not at all aware of his or her surroundings for a very long time.