Definition of "radon" [ra•don]

• A colorless, radioactive, inert gaseous element formed by the radioactive decay of radium. It is used as a radiation source in radiotherapy and to produce neutrons for research. Its most stable isotope is Rn 222 with a half-life of 3.82 days. Atomic number 86; melting point -71°C; boiling point -61.8°C; specific gravity (solid) 4. See Table at element. (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.

• "Checking for radon is an inexpensive task using one of the short - or long-term radon test kits we reviewed."
• "The resulting microscopic particles were known as radon “daughters,” and the daughters were all radioactive, too."
• "Usually, radon is found in your basement (underground deposits of uranium decay and produce the gas) -- but when the radon specialist inspected Dr. Sugarman's house -- he found radon in her kitchen."