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WordNet
ethyl group

n. the univalent hydrocarbon radical C2H5 derived from ethane by the removal of one hydrogen atom [syn: ethyl, ethyl radical]

Wikipedia
Ethyl group

In chemistry, an ethyl group is an alkyl substituent derived from ethane ( C H). It has the formula – C H C H and is very often abbreviated Et. Ethyl is used in the IUPAC nomenclature of organic chemistry for a saturated two-carbon moiety in a molecule, whilst the prefix "eth-" is used to indicate the presence of two carbon atoms in the molecule.