Polyphasic sleep is a sleep pattern in which a person’s total daily sleep is divided into multiple shorter sleep periods distributed throughout the day, as opposed to the more conventional monophasic pattern of a single consolidated block of sleep at night. The term comes from the Greek “poly” (many) and the Latin “phasic” (phases or stages). In polyphasic sleep schedules, the sleeper aims to take several shorter naps or sleep periods throughout the day and night, rather than one long nighttime sleep. Various polyphasic schedules have been devised, ranging from biphasic sleep (two main sleep periods per day, such as a shorter nighttime sleep combined with an afternoon siesta) to more extreme schedules such as the Uberman (six 20-minute naps evenly distributed every four hours, totaling just two hours of sleep per day) or the Everyman (one core nighttime sleep of about three hours combined with several daytime naps). Proponents of extreme polyphasic schedules claim they can significantly reduce total sleep time while maintaining adequate alertness and functioning. However, the scientific evidence supporting these claims is limited, and most sleep researchers caution that such schedules are difficult to sustain and may result in cumulative sleep deprivation, impaired cognitive function, and negative health consequences. More moderate forms of polyphasic sleep, such as biphasic sleep (a shorter nighttime sleep with an afternoon nap), are more compatible with human biology and are practiced by many cultures around the world. Research suggests that an afternoon nap of 10 to 30 minutes can improve alertness and cognitive performance without impairing nighttime sleep.