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Also known as Radioactive Decay. Radioactive substances undergo radioactive decay, the rate of which is determined by the properties of the radionuclide. As decay proceeds the resulting activity of the parent Nuclide reduces and will eventually disappear. The daughter product may be stable (inactive) or may itself be Radioactive and undergo further decay (i.e. as part of a decay series). The rate of decay can be expressed in terms of its Half-Life (the time taken for the activity to reduce by half).

Reality is merely an illusion, albeit a very persistent one

– Albert Einstein