NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,804 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.

methyl group
(MEH-thul groop)
A small molecule made of one carbon and three hydrogen atoms. Methyl groups are added or removed from proteins or nucleic acids and may change the way these molecules act in the body.