ethyl radical vs alkyl group

ethyl radical and alkyl group both are nouns.

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

As nouns, alkyl group is a hypernym of ethyl radical; that is, alkyl group is a word with a broader meaning than ethyl radical:

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

Other hypernyms of ethyl radical include alkyl, alkyl radical.

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