tailfin vs decoration

tailfin and decoration both are nouns.

Word	Noun	Adjective	Verb	Adverb
tailfin	Yes	No	No	No
decoration	Yes	No	No	No

As nouns, decoration is a hypernym of tailfin; that is, decoration is a word with a broader meaning than tailfin:

tailfin: one of a pair of decorations projecting above the rear fenders of an automobile
decoration: something used to beautify

Other hypernyms of tailfin include ornament, ornamentation.

tailfin (noun)	decoration (noun)
a stabilizer that is part of the vertical tail structure of an airplane	the act of decorating something (in the hope of making it more attractive)
one of a pair of decorations projecting above the rear fenders of an automobile	something used to beautify
	an award for winning a championship or commemorating some other event