Radioactivity is the spontaneous emission of radiation in the form of particles or high energy photons resulting from a nuclear reaction. It is also known as radioactive decay, nuclear decay, nuclear disintegration, or radioactive disintegration. While there are many forms of electromagnetic radiation, they are not always produced by radioactivity.
For example, a light bulb may emit radiation in the forms of heat and light, yet it is not radioactive. A substance that contains unstable atomic nuclei is considered to be radioactive.
