ornament vs tail fin

ornament and tail fin both are nouns.

Word	Noun	Adjective	Verb	Adverb
ornament	Yes	No	Yes	No
tail fin	Yes	No	No	No

As nouns, tail fin is a hyponym of ornament; that is, tail fin is a word with a more specific, narrower meaning than ornament:

ornament: something used to beautify
tail fin: one of a pair of decorations projecting above the rear fenders of an automobile

ornament (noun)	tail fin (noun)
something used to beautify	the tail of fishes and some other aquatic vertebrates
	a stabilizer that is part of the vertical tail structure of an airplane
	one of a pair of decorations projecting above the rear fenders of an automobile

ornament (verb)	tail fin (verb)
make more attractive by adding ornament, colour, etc.
be an ornament to