Somnology Study is the scientific study of sleep. It involves researching the biological, psychological, and social aspects of sleep, as well as the diagnosis and treatment of sleep disorders. The term 'somnology' is derived from the Latin word somnus, meaning 'sleep'. The study of sleep is an important part of understanding how the body and mind function, and can help to improve overall health and wellbeing. The five-letter answer to the crossword puzzle is SLEEP, which is a key component of somnology study.