The term SLEEP(PREF) can be broken down into two parts: the prefix 'sleep' and the suffix '(pref)'. The prefix 'sleep' is a noun that refers to a natural, regular, and necessary state of rest or inactivity. The suffix '(pref)' indicates that the two crossword solutions are related to this term. The two crossword solutions for this term are NARCO and HYPNO, both of which are five letters long. NARCO is an abbreviation for narcotics, which are drugs that induce sleep or a state of unconsciousness. HYPNO is an abbreviation for hypnosis, which is a trance-like state of consciousness that is induced by a hypnotist and can be used to help people relax and fall asleep.