Definition of "melatonin" []

• A hormone derived from serotonin and produced by the pineal gland that stimulates color change in the epidermis of amphibians and reptiles and plays a role in sleep, aging, and reproduction in mammals. (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.

• "Now, you probably also know the word melatonin because in supplement form it’s often used as a sleep aid, and for good reason."
• "This article on sleep and melatonin is also available at Dr. Breus's official blog, The Insomnia Blog."
• "Many supplement companies and health food stores will claim that melatonin is a natural sleeping aid or nightcap because it "naturally" helps regulate sleep-wake cycles."