Deep sleep is a state of unconsciousness that is characterized by a lack of responsiveness to external stimuli. It is a natural part of the sleep cycle and can be divided into four stages: COMA (4 letters), SOPOR (5 letters), REM (3 letters), TRANCE (6 letters), and SNORE (5 letters). COMA is the deepest stage of sleep, where the body is completely relaxed and the brain activity is minimal. SOPOR is a lighter stage of sleep, where the body is still relaxed but the brain is more active. REM stands for Rapid Eye Movement, which is a stage of sleep where the eyes move rapidly and the brain is highly active. TRANCE is a state of deep relaxation, where the body is still and the mind is focused. Finally, SNORE is a sound made when breathing during sleep.