tail fin vs caudal fin

tail fin and caudal fin both are nouns.

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

As nouns, tail fin and caudal fin are synonyms defined as:

tail fin and caudal fin: the tail of fishes and some other aquatic vertebrates

tail fin (noun)	caudal fin (noun)
the tail of fishes and some other aquatic vertebrates	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