radioactive decay

noun Physics.

1. decay(def 8).

noun

1. disintegration of a nucleus that occurs spontaneously or as a result of electron capture. One or more different nuclei are formed and usually particles and gamma rays are emittedSometimes shortened to: decay Also called: disintegration

1. The spontaneous transformation of an unstable atomic nucleus into a lighter one, in which radiation is released in the form of alpha particles, beta particles, gamma rays, and other particles. The rate of decay of radioactive substances such as carbon 14 or uranium is measured in terms of their half-life. See also decay radioisotope.