follow up vs action

follow up is not a noun while action is a noun.

Word	Noun	Adjective	Verb	Adverb
follow up	No	No	Yes	No
action	Yes	No	Yes	No

follow up (noun)	action (noun)
	the most important or interesting work or activity in a specific area or field
	a judicial proceeding brought by one party against another; one party prosecutes another for a wrong done or for protection of a right or for prevention of a wrong
	something done (usually as opposed to something said)
	a military engagement
	an act by a government body or supranational organization
	the operating part that transmits power to a mechanism
	In firearms terminology, the mechanism that handles the ammunition (loads, locks, fires, and extracts the cartridges).
	the trait of being active and energetic and forceful
	the series of events that form a plot
	a process existing in or produced by nature (rather than by the intent of human beings)
	the state of being active

follow up (verb)	action (verb)
pursue to a conclusion or bring to a successful issue	put in effect
increase the effectiveness or success of by further action	institute legal proceedings against; file a suit against