homocercal fin vs tail fin

homocercal fin and tail fin both are nouns.

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

As nouns, tail fin is a hypernym of homocercal fin; that is, tail fin is a word with a broader meaning than homocercal fin:

homocercal fin: symmetrical tail fin extending beyond the end of the vertebral column as in most bony fishes
tail fin: the tail of fishes and some other aquatic vertebrates

Other hypernyms of homocercal fin include caudal fin.

homocercal fin (noun)	tail fin (noun)
symmetrical tail fin extending beyond the end of the vertebral column as in most bony fishes	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