chase after vs romance

chase after is not a noun while romance is a noun.

Word	Noun	Adjective	Verb	Adverb
chase after	No	No	Yes	No
romance	Yes	No	Yes	No

As verbs, romance is a hypernym of chase after; that is, romance is a word with a broader meaning than chase after:

Other hypernyms of chase after include court, solicit, woo.

chase after (noun)	romance (noun)
	an exciting and mysterious quality (as of a heroic time or adventure)
	a novel dealing with idealized events remote from everyday life
	a story dealing with love
	a relationship between two lovers

chase after (verb)	romance (verb)
go after with the intent to catch	tell romantic or exaggerated lies
pursue someone sexually or romantically	talk or behave amorously, without serious intentions
	have a love affair with
	make amorous advances towards