Fundulus majalis vs mayfish

Fundulus majalis and mayfish both are nouns.

Word	Noun	Adjective	Verb	Adverb
Fundulus majalis	Yes	No	No	No
mayfish	Yes	No	No	No

As nouns, Fundulus majalis and mayfish are synonyms defined as:

Fundulus majalis and mayfish: black-barred fish of bays and coastal marshes of the Atlantic and Gulf Coast of the United States

Other synonyms of Fundulus majalis include may fish, striped killifish.

Fundulus majalis (noun)	mayfish (noun)
black-barred fish of bays and coastal marshes of the Atlantic and Gulf Coast of the United States	black-barred fish of bays and coastal marshes of the Atlantic and Gulf Coast of the United States