caffein
/kæˈfiːn/
noun
- A bitter stimulant drug found in coffee, tea, and some other drinks, which makes people feel more awake and energetic.
- Some sodas and energy drinks contain high levels of caffein.
- Too much caffein can make you feel jittery or keep you awake at night.
- Many people drink coffee for the caffein to help them wake up in the morning.