biphasic sleep

biphasic sleep (uncountable)

1. The practice of sleeping twice per night, interrupted by a period of wakefulness; common in the days before electric lighting during the season with longer night.
   • 2022 January 27, Derek Thompson, “Can Medieval Sleeping Habits Fix America’s Insomnia?”, in The Atlantic‎:

     Beginning in the 1700s, the industrial revolution—its light, its caffeine, its clocks, and above all, its work schedules—took Europe’s biphasic sleep in its hairy arms and mushed the two phases together.

2. The practice of taking a regular nap during the afternoon and sleeping fewer hours at night.