Español
Questions About Cancer? 1-800-4-CANCER
  • Print
  • Facebook
  • Twitter
  • Google+
  • Pinterest

NCI Dictionary of Cancer Terms


free radical  listen  (free RA-dih-kul)

  A type of unstable molecule that is made during normal cell metabolism (chemical changes that take place in a cell). Free radicals can build up in cells and cause damage to other molecules, such as DNA, lipids, and proteins. This damage may increase the risk of cancer and other diseases.