Radiation
Part of speech: noun
Definition: The shooting forth of anything from a point or surface, like the diverging rays of light; as, the radiation of heat. The process of radiating waves or particles. The transfer of energy via radiation (as opposed to convection or conduction) Radioactive energy
Example sentence: Since we can produce all types of light by means of hot bodies, we can ascribe, to the radiation in thermal equilibrium with hot bodies, the temperature of these bodies, and thus every radiation, even that issuing from a phosphorescent body, has a certain temperature for every colour.
Radioactivity
Part of speech: noun
Definition: Spontaneous emission of ionizing radiation as a consequence of a nuclear reaction, or directly from the breakdown of an unstable nucleus.The radiation so emitted; including gamma rays, alpha particles, neutrons, electrons, positrons, etc.