IM general only for principle of emission of radiations; NIM as coordinate for degree of radioactivity of specific radioelements or radioisotopes (IM); do not use as routine coordinate for amount of radiation or degree of radioactivity of radioisotope tracers; entry term NUCLEAR DECAY: coordinate NIM with specific radioactive substance (IM) & do not add RADIOMETRY

The spontaneous transformation of a nuclide into one or more different nuclides, accompanied by either the emission of particles from the nucleus, nuclear capture or ejection of orbital electrons, or fission. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)