Consciousness means being awake, alert and responsive to the environment. The definition of consciousness may differ in psychology, neuroscience, philosophy and other related sciences. It is often disputed amongst academics and scientists.

Consciousness is a range of mental states. There are several states between a fully conscious state and a fully unconscious state. In medicine, the degree of loss of consciousness is measured by using Glasgow Coma Scale (GCS); a score between 3 and 15 is given to each person at any time, to show how conscious he or she is. Higher scores show more conscious states.