"Sleep latency" refers to the time it takes for a person to fall asleep after getting into bed. It measures how quickly someone can transition from being awake to asleep. Full definition
Multiple sleep latency tests which measured how quickly the children fell asleep (four times twenty minutes on the same day). (sciencedaily.com)
Afifi L, Kushida C.A., Carskadon M.A. Multiple Sleep Latency Test (MSLT). (lifespan.org)
Short - term treatment (up to three months) of prolonged - release melatonin was found to be effective and safe in improving sleep latency, sleep quality, and daytime alertness. (en.wikipedia.org)