1. A bitter crystallizable substance obtained from coffee.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• coffeine,
• cafene,
• coffeie,
• caffeeine,
• cafine,
• caffenine,
• caffiene,
• caffenee,
• caffieeine,
• cafeine,
• caffen,
• caffine,
• caffeinie,
• caffenie,
• caffeiene,
• cafeinee,
• caffeien,
• cafiene,
• caffefine,
• caffaine

• caffein,
• coffin,
• Cavin,
• cave in,
• caffeinate,
• cabin,
• cave-in.

The adjective form of the word "caffeine" is "caffeinated".

The plural of the "caffeine" can be the "caffeines".

The singular of the "caffeine" can be the "caffeine".