caudal fin(n = noun.animal) tail fin - the tail of fishes and some other aquatic vertebrates;
is a kind of fin
is a part of fish
has particulars: heterocercal fin, homocercal fin

caudal, caudal anaesthesia, caudal anesthesia, caudal appendage, caudal block, caudal vertebra, dorsal fin, fin, fin de si'8acle, fin de siecle, fin keel, fin whale, heterocercal fin, homocercal fin, pectoral fin, pelvic fin, tail fin, ventral fin, vertical fin