black whale vs sperm whale

black whale and sperm whale both are nouns.

Word	Noun	Adjective	Verb	Adverb
black whale	Yes	No	No	No
sperm whale	Yes	No	No	No

As nouns, black whale and sperm whale are synonyms defined as:

black whale and sperm whale: large whale with a large cavity in the head containing spermaceti and oil; also a source of ambergris

Other synonyms of black whale include cachalot, Physeter catodon.

black whale (noun)	sperm whale (noun)
large whale with a large cavity in the head containing spermaceti and oil; also a source of ambergris	large whale with a large cavity in the head containing spermaceti and oil; also a source of ambergris
small dark-colored whale of the Atlantic coast of the United States; the largest male acts as pilot or leader for the school