Sleep glossary

Sleep cycle

~90-minute period including light, deep, and REM sleep stages.

REM

Rapid Eye Movement — dream stage and memory processing.

Sleep latency

Minutes between getting in bed and falling asleep (avg. 14 min).

Sleep inertia

Grogginess when waking from deep sleep — confused, sluggish feeling.

Power nap

Short 15–26 min nap avoiding deep sleep stages.

Chronotype

Biological preference: morning lark vs. night owl.

Sleep debt

Accumulated sleep loss over multiple nights.