methane series vs C2H6

methane series and C2H6 both are nouns.

Word	Noun	Adjective	Verb	Adverb
methane series	Yes	No	No	No
C2H6	Yes	No	No	No

As nouns, C2H6 is a hyponym of methane series; that is, C2H6 is a word with a more specific, narrower meaning than methane series:

methane series: a series of non-aromatic saturated hydrocarbons with the general formula CnH(2n+2)
C2H6: a colorless odorless alkane gas used as fuel

Other hyponyms of methane series include butane, amine, aminoalkane, ethane, heptane, hexane, methane.

methane series (noun)	C2H6 (noun)
a series of non-aromatic saturated hydrocarbons with the general formula CnH(2n+2)	a colorless odorless alkane gas used as fuel