Written by the Fiveable Content Team โข Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 examโขWritten by the Fiveable Content Team โข Last updated September 2025
Definition
Also known as deep sleep or slow-wave sleep, this is the third stage in the cycle of non-rapid eye movement (NREM) sleep, during which the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system.
Related terms
Rapid Eye Movement (REM) Sleep: This is a stage of sleep characterized by rapid eye movements, more dreaming and bodily movement, and faster pulse and breathing.