/ iˈmɪʃn; NAmE / noun
1.
[ U ] ( formal ) the production or sending out of light, heat, gas, etc. :
the emission of carbon dioxide into the atmosphere
emission controls
2.
[ C ] gas, etc. that is sent out into the air :
The government has pledged to clean up industrial emissions.
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WORD ORIGIN
late Middle English (in the sense emanation ): from Latin emissio(n-) , from emiss- sent out, from the verb emittere , from e- (variant of ex- ) out of + mittere send.