P.A. vs PA system

P.A. and PA system both are nouns.

Word	Noun	Adjective	Verb	Adverb
P.A.	Yes	No	No	No
PA system	Yes	No	No	No

As nouns, P.A. and PA system are synonyms defined as:

P.A. and PA system: an electronic amplification system used as a communication system in public areas

Other synonyms of P.A. include P.A. system, PA, public address system.

P.A. (noun)	PA system (noun)
an electronic amplification system used as a communication system in public areas	an electronic amplification system used as a communication system in public areas