petty officer vs PO

petty officer and PO both are nouns.

Word	Noun	Adjective	Verb	Adverb
petty officer	Yes	No	No	No
PO	Yes	No	No	No

As nouns, petty officer and PO are synonyms defined as:

petty officer and PO: a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army

Other synonyms of petty officer include P.O..

petty officer (noun)	PO (noun)
a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army	an independent agency of the federal government responsible for mail delivery (and sometimes telecommunications) between individuals and businesses in the United States
	a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army