Level of consciousness is a term used to describe a person's awareness and understanding of what is happening in his or her surroundings.
There are three main levels of consciousness:
Consciousness is an awake state, when a person is fully aware of his or her surroundings and understands, talks, moves, and responds normally.
Decreased consciousness is when a person appears to be awake and aware of surroundings (conscious) but is not responding normally. While in a state of decreased consciousness, a person may not answer when spoken to, stare straight ahead, and have no facial expression. Others may think the person is acting confused, odd, or sleepy. Later, the person may not be able to recall what happened.
Unconsciousness is when a person is not aware of what is going on and is not able to respond normally to things that happen to and around him or her.
Fainting is a brief form of unconsciousness.
Coma is a deep, prolonged state of unconsciousness.
General anesthesia is a controlled period of unconsciousness.