NCI Dictionary of Cancer Terms
The NCI Dictionary of Cancer Terms features 7,926 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.
- listen (RAY-dee-AY-shun)
- Energy released in the form of particle or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, medical x-rays, and energy given off by a radioisotope (unstable form of a chemical element that releases radiation as it breaks down and becomes more stable).