computer science vs security system

computer science and security system both are nouns.

Word	Noun	Adjective	Verb	Adverb
computer science	Yes	No	No	No
security system	Yes	No	No	No

computer science (noun)	security system (noun)
the branch of engineering science that studies (with the aid of computers) computable processes and structures	an electrical device that sets off an alarm when someone tries to break in
	(computing) a system that enforces boundaries between computer networks