kitty vs domestic cat

kitty and domestic cat both are nouns.

Word	Noun	Adjective	Verb	Adverb
kitty	Yes	No	No	No
domestic cat	Yes	No	No	No

As nouns, domestic cat is a hypernym of kitty; that is, domestic cat is a word with a broader meaning than kitty:

Other hypernyms of kitty include Felis catus, Felis domesticus, house cat.

kitty (noun)	domestic cat (noun)
informal terms referring to a domestic cat	any domesticated member of the genus Felis
young domestic cat
the combined stakes of the betters
the cumulative amount involved in a game (such as poker)