-on¹
suff.

1. 1. Subatomic particle: baryon.
   2. Unit; quantum: photon.
2. Basic hereditary unit: codon.

[From ION.]

-on²
suff.
Inert gas: radon.

[New Latin, from (ARG)ON.]

-on³
suff.
A chemical compound that is not a ketone or a compound that contains oxygen in a carbonyl group: parathion.

[Alteration of -ONE.]

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The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

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