When you're drowsy, you feel sleepy and struggle to keep your eyes open. Your eyelids feel heavy, your thoughts get fuzzy, and staying alert takes real effort. A long car ride on a warm afternoon might make you drowsy, or sitting in a quiet room after lunch when your body wants to rest.

Drowsiness is that in-between state where you're not quite awake and not quite asleep. You might notice yourself yawning, your head nodding forward, or losing track of what you were reading. Some medicines warn that they may cause drowsiness, meaning they might make you feel sleepy as a side effect.

Being drowsy at bedtime is perfectly normal, but feeling drowsy at the wrong times (like during an important class) can mean you need more sleep at night. When you're drowsy while driving or doing something that requires attention, it's safer to stop and rest.