Consciousness comes from the Latin word “conscientia” which means “knowledge-within”, or knowledge that is shared. Today the term is used to describe the experience of “self” as distinct from the external environment. It is characterized by experiences of alertness, self-awareness, and attention of oneself relative to the environment relative to the self; i.e., identify, which in turn involves awareness of one’s own perceptions, associations, emotional experience, and the cognitive interpretation of these experiences. More narrowly, consciousness is often defined level of arousal, wakefulness, alertness, responsiveness, and adaptability in contrast to states of coma or sleep.
However, consciousness has defied unitary definition, perhaps because it is intrinsically bound to subjective experience.