act of terrorism vs Sep 11

act of terrorism and Sep 11 both are nouns.

Word	Noun	Adjective	Verb	Adverb
act of terrorism	Yes	No	No	No
Sep 11	Yes	No	No	No

act of terrorism (noun)	Sep 11 (noun)
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	the day in 2001 when Arab suicide bombers hijacked United States airliners and used them as bombs