Definition of "caffeine" []

• A bitter white alkaloid, C8H10N4O2, often derived from tea or coffee and used in medicine chiefly as a mild stimulant and to treat certain kinds of headache. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "While none of the participants were given a drink high in caffeine, the researchers concluded that caffeine is probably more helpful than sugar in staying alert."
• "After oil, caffeine is the biggest driver of our economy."
• "No caffeine is allowed on the day of the exam, before the test is completed."