NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,790 terms related to cancer and medicine.

Browse the dictionary by selecting a letter of the alphabet or by entering a cancer-related word or phrase in the search box.

melatonin
(MEH-luh-TOH-nin)
A hormone made by the pineal gland (tiny organ near the center of the brain). Melatonin helps control the body’s sleep cycle, and is an antioxidant. It is also made in the laboratory and sold as a supplement.