睡 sleep

We say "SWEET dreams" when we go to sleep.

The sleepy guy's eyelids looked like they were dangling and about to fall closed.

sleep ★★☆☆☆ NP
睡 (sleep) + 眠 (sleepy) = 睡眠 (sleep )

a somewhat medical-sounding word for sleep (BOOBOO: you would never say, "よく睡眠した?" -You gotta say, "よくねた?")

sleeping pill ★☆☆☆☆
睡眠 (sleep ) + 薬 (medicine) = 睡眠薬 (sleeping pill)