Definition of CASTLE for Kids. 1. : a large building or group of buildings usually having high walls with towers that was built in the past to protect against attack. 2. : a large or impressive house.ull Definition of CASTLE. 1. a: a large fortified building or set of buildings b: a massive or imposing house. 2. : a retreat safe against intrusion or invasion. 3. : 3rook. See castle defined for English-language learners.
The Science of Sleep. Sleep is one of the strangest things we do each day. The average adult will spend 36 percent of his or her life asleep. For one-third of our time on earth, we transition from the vibrant, thoughtful, active organisms we are during the day and power down into a quiet state of hibernation.
Light and Deep Sleep. During sleep, you alternate between cycles of REM (rapid eye movement) and NREM (non-rapid eye movement) that repeat about every 90 minutes. You spend about 75 percent of the night in NREM sleep, which consists of four stages of increasing relaxation. Stage one, or the phase between being awake and asleep, is considered light sleep. Deeper sleep begins in stage two, as your breathing and heart rate become regular and your body temperature drops.