Rapid Eye Movement Sleep %28REM%29
Here's your citation in American Psychological Association (APA) format:
Rapid Eye Movement Sleep %28REM%29. (n.d.). In Alleydog.com's online glossary. Retrieved from: https://www.alleydog.com/glossary/definition-cit.php?term=Rapid+Eye+Movement+Sleep+%2528REM%2529