reign of terror vs terrorism

reign of terror and terrorism both are nouns.

Word	Noun	Adjective	Verb	Adverb
reign of terror	Yes	No	No	No
terrorism	Yes	No	No	No

reign of terror (noun)	terrorism (noun)
any period of brutal suppression thought to resemble the Reign of Terror in France	the calculated use of violence (or the threat of violence) against civilians in order to attain goals that are political or religious or ideological in nature; this is done through intimidation or coercion or instilling fear