Ethyl group - Wikipedia
https://en.wikipedia.org/wiki/Ethyl_groupIn chemistry, an ethyl group is an alkyl substituent derived from ethane (C2H6). It has the formula –CH2CH3 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, while the prefix "eth-" is used to indicate the presence of two carbon atoms in the molecule.