tomcat vs Felis catus

tomcat and Felis catus both are nouns.

Word	Noun	Adjective	Verb	Adverb
tomcat	Yes	No	No	No
Felis catus	Yes	No	No	No

As nouns, Felis catus is a hypernym of tomcat; that is, Felis catus is a word with a broader meaning than tomcat:

Other hypernyms of tomcat include domestic cat, Felis domesticus, house cat.

tomcat (noun)	Felis catus (noun)
male cat	any domesticated member of the genus Felis