alkyl group vs ethyl

alkyl group and ethyl both are nouns.

Word	Noun	Adjective	Verb	Adverb
alkyl group	Yes	No	No	No
ethyl	Yes	No	No	No

As nouns, ethyl is a hyponym of alkyl group; that is, ethyl is a word with a more specific, narrower meaning than alkyl group:

alkyl group: any of a series of univalent groups of the general formula CnH2n+1 derived from aliphatic hydrocarbons
ethyl: the univalent hydrocarbon radical C2H5 derived from ethane by the removal of one hydrogen atom

Other hyponyms of alkyl group include ethyl group, ethyl radical, methyl, methyl group, methyl radical.

alkyl group (noun)	ethyl (noun)
any of a series of univalent groups of the general formula CnH2n+1 derived from aliphatic hydrocarbons	the univalent hydrocarbon radical C2H5 derived from ethane by the removal of one hydrogen atom