1. Any substance that flows out or is emitted from a source or origin. 2. The radiation from a radioactive element. [L. e- mano, pp. -atus, to flow out]
- actinium e. radon-219. See emanon.
- radium e. radon-222. See emanon.
- thorium e. radon-220. See emanon.

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em·a·na·tion .em-ə-'nā-shən n
1) the action of emanating
2 a) something that emanates or is produced by emanation
b) a heavy gaseous element produced by radioactive disintegration <radium \emanation>

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em·a·na·tion (em″ə-naґshən) [L. e out + manare to flow] that which is given off, such as a gaseous disintegration product given off from radioactive substances.

Medical dictionary. 2011.