radioactive decay(redirected from Activity (radioactivity))
Also found in: Dictionary, Thesaurus, Encyclopedia.
the disintegration of the nucleus of an unstable nuclide by the spontaneous emission of charged particles, photons, or both.
The continual loss of energy by radioactive substances. Disintegration of the nucleus by the emission of alpha, beta, or gamma rays eventually results in the complete loss of radioactivity. The time required for some materials to become stable may be minutes and, for others, thousands of years.See: half-life
See also: decay
characterized by radioactivity.
spontaneous decomposition of the nuclei of the atoms of radioactive substances. Measured as the proportion of the atoms in a radionuclide that decompose per unit of time, usually stated as the half-life of that particular isotope.
dissemination of radioactive substances through the atmosphere and deposition on the environment generally; causes radiation injury.
radionuclide. A radioactive nuclide, e.g. radioactive iodine or strontium.
see radioactive tracer.