Because of a lapse in government funding, the information on this website may not be up to date transactions submitted via the website may not be processed, and the agency may not be able to respond to inquiries until appropriations are enacted.

The NIH Clinical Center (the research hospital of NIH) is open. For more details about its operating status, please visit cc.nih.gov.

Updates regarding government operating status and resumption of normal operations can be found at USA.gov.

NCI Dictionary of Cancer Terms

  • Resize font
  • Print
  • Email
  • Facebook
  • Twitter
  • Google+
  • Pinterest

The NCI Dictionary of Cancer Terms features 8,188 terms related to cancer and medicine.

We offer a widget that you can add to your website to let users look up cancer-related terms. Get NCI’s Dictionary of Cancer Terms Widget.

Browse:
sleep stage
(sleep stayj)
One of 5 parts or stages of the sleep cycle based on the type of brain activity that occurs during the stage. During stages 1 to 4, a person will feel drowsy, fall asleep, and move into a deep, dreamless sleep. Stage 5 is called rapid eye movement (REM) sleep, and it is during this stage that dreams occur. During several hours of normal sleep, a person will go through several sleep cycles that include REM sleep and the 4 stages of non-REM sleep (light to deep sleep).